Transpile template using babel

[lmiller1990]

The new @vue/compiler-sfc generates code using ES module syntax. It is causing some problems with vue-cli: vuejs/vue-cli#5714 (comment)

Easy fix is just use babel to compile the template code to commonjs module syntax. The idea for v5 was to be entirely ts-jest based, although even if I set target: es5 etc in tsconfig.json I could not get it to work. This seems like the best solution, so people can use VTU and vue-jest with vue-cli out of the box.

Testing

I tested this in a pretty primitive manner: create a new cli project:

Vue CLI v4.5.0
? Please pick a preset: Manually select features
? Check the features needed for your project: Choose Vue version, Babel, TS, Unit
? Choose a version of Vue.js that you want to start the project with 3.x (Preview)
? Use class-style component syntax? No
? Use Babel alongside TypeScript (required for modern mode, auto-detected polyfills, t
ranspiling JSX)? Yes
? Pick a unit testing solution: Jest
? Where do you prefer placing config for Babel, ESLint, etc.? In dedicated config file
s

Note I included babel and TypeScript and testing with jest.

Then yarn test:unit --no-cache and it failed. Then I just copy and pasted the new vue-jest from the PR into node_modules and ran yarn test:unit --no-cache and it passed. As long as CI passes, we should be good.

resolves #258

[lmiller1990]

It's out