feat: add custom transform

[fsdiogo]

This PR adds the ability to customise transforms to be used to relocate the dropdown.

It will be used in ipfs/ipfs-webui#929.

/cc @olizilla

[olizilla]

Nice and simple 👍

Please add an example of a transform usage to the examples page. Can you add also add parcel@1.9.7 as a dev dependecy, looks like I missed that, and its needed to make npm start work out of the box.

[fsdiogo]

Done!

Also switched from babel-preset-react to @babel/preset-react because it was breaking the examples.

[olizilla]

npm run build is failing for me. I have tried rimraffing my node_modules and re-installing

$ npm run build

> @tableflip/react-dropdown@1.1.1 build /Users/oli/Code/tableflip/react-dropdown
> run-s clean build:*


> @tableflip/react-dropdown@1.1.1 clean /Users/oli/Code/tableflip/react-dropdown
> rm -rf docs/* lib/*


> @tableflip/react-dropdown@1.1.1 build:js /Users/oli/Code/tableflip/react-dropdown
> babel src/index.js -o lib/index.js

Error: Requires Babel "^7.0.0-0", but was loaded with "6.26.3". If you are sure you have a compatible version of @babel/core, it is likely that something in your build process is loading the wrong version. Inspect the stack trace of this error to look for the first entry that doesn't mention "@babel/core" or "babel-core" to see what is calling Babel. (While processing preset: "/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/preset-react/lib/index.js")
    at throwVersionError (/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/helper-plugin-utils/lib/index.js:65:11)
    at Object.assertVersion (/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/helper-plugin-utils/lib/index.js:13:11)
    at _default (/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/preset-react/lib/index.js:61:7)
    at /Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/helper-plugin-utils/lib/index.js:19:12
    at /Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/options/option-manager.js:317:46
    at Array.map (<anonymous>)
    at OptionManager.resolvePresets (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/options/option-manager.js:275:20)
    at OptionManager.mergePresets (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/options/option-manager.js:264:10)
    at OptionManager.mergeOptions (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/options/option-manager.js:249:14)
    at OptionManager.init (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/options/option-manager.js:368:12)
    at File.initOptions (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/index.js:212:65)
    at new File (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/file/index.js:135:24)
    at Pipeline.transform (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-core/lib/transformation/pipeline.js:46:16)
    at transform (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/util.js:50:22)
    at Object.compile (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/util.js:59:12)
    at /Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/file.js:142:23
    at Array.forEach (<anonymous>)
    at walk (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/file.js:133:16)
    at files (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/file.js:156:7)
    at module.exports (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/file.js:184:5)
    at Object.<anonymous> (/Users/oli/Code/tableflip/react-dropdown/node_modules/babel-cli/lib/babel/index.js:129:1)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @tableflip/react-dropdown@1.1.1 build:js: `babel src/index.js -o lib/index.js`
npm ERR! Exit status 1

[fsdiogo]

Sorry, missed the babel-cli => @babel/cli. It should be working now!

[olizilla]

almost... perhaps the lib dir needs to exist first?

> @tableflip/react-dropdown@1.1.1 build:js /Users/oli/Code/tableflip/react-dropdown
> babel src/index.js -o lib/index.js

{ Error: ENOENT: no such file or directory, open 'lib/index.js'
    at Object.openSync (fs.js:436:3)
    at Object.writeFileSync (fs.js:1168:35)
    at output (/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/cli/lib/babel/file.js:148:23)
    at /Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/cli/lib/babel/file.js:234:9
    at Generator.next (<anonymous>)
    at asyncGeneratorStep (/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/cli/lib/babel/file.js:74:103)
    at _next (/Users/oli/Code/tableflip/react-dropdown/node_modules/@babel/cli/lib/babel/file.js:76:194)
  errno: -2,
  syscall: 'open',
  code: 'ENOENT',
  path: 'lib/index.js' }

[fsdiogo]

Yeah, the folder had to exist.

Now using the -d option that creates the folder if it doesn't exist.

[olizilla]

LGTM