tx-browser: Parcel breaks tx-browser Netlify deploy

[epost]

In #344, I found that parcel was causing the Netlify builds to fail, seemingly due to tx-browser/html/index.css referencing css and svg files in ../../studio/html. The build error was:

1:14:48 PM: 🚨  /opt/build/repo/halogen-grid-kit/src/GridKit/KeyHandler.css:undefined:undefined: Cannot find module 'cssnano' from '/opt/build/repo/halogen-grid-kit/src/GridKit'
1:14:48 PM:     at /opt/build/repo/tx-browser/node_modules/resolve/lib/async.js:107:35
1:14:48 PM:     at processDirs (/opt/build/repo/tx-browser/node_modules/resolve/lib/async.js:260:39)
1:14:48 PM:     at isdir (/opt/build/repo/tx-browser/node_modules/resolve/lib/async.js:267:32)
1:14:48 PM:     at /opt/build/repo/tx-browser/node_modules/resolve/lib/async.js:23:69
1:14:48 PM:     at FSReqWrap.oncomplete (fs.js:153:21)

The files are referenced here:

• (https://github.com/statebox/purescript-studio/pull/346/files#diff-2b91eab53cc50180839a81a1c9e9c7baR5-R10)
• https://github.com/statebox/purescript-studio/pull/346/files#diff-2b91eab53cc50180839a81a1c9e9c7baR29

Some builds in which this failed:

• 5e42d7b31d346a0008dd2c30
• 5e4297c1f91836000910eb18
• 5e4290e7f1499f01df7b33ca.

A workaround was to copy the files into the tx-browser/html dir, rather than referencing them in ../../studio/html. Therefore, the referencing was reverted here:

• 63a1e27

This seems to be related to Parcel issue #2881.

However, this isn't really what we want.

Reproduction steps

• Push a change to tx-browser to `development and wait for its deploy to finish: https://app.netlify.com/sites/dazzling-albattani-1c9272/deploys. NB: This is not the same thing as the studio Netlify site.
• When the deploy is finished, visit it here: https://browse.statebox.cloud, aka https://dazzling-albattani-1c9272.netlify.com.

If you are going to be testing this, it would probably be better to configure the tx-browser site such that it wouldn't just be triggered by deploys to development, but also by commits to PR branches.

To try

• Use Rollup? Rollup is for js only, you can't point it to an html file like parcel.
  • Cat css files and pipe through PostCSS
• Use Parcel 2.0.0-alpha? Can't get it to work