(Naively) attempt to replace babel & terser with esbuild

[Johennes]

This is a naive and uninformed experiment that replaces babel and terser with esbuild (which, among others, is used by Vite for external dependencies).

On my MacBook a clean yarn build takes ~70s before and ~40s after this change. Some of this gain might be undone or outweighed by the caveats listed below.

Caveats & things to figure out

• esbuild doesn't currently support browserslist and I wasn't sure what to set the target option to
• I assume some or all of the settings in https://github.com/vector-im/element-web/blob/develop/babel.config.js would have to be applied to esbuild
• esbuild automatically uses tsconfig.json but doesn't support all of its options
• esbuild doesn't do any type checking neither does babel

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This change is marked as an internal change (Task), so will not be included in the changelog.

[t3chguy]

esbuild doesn't do any type checking

Neither does babel, it relies on you running tsc yourself.

https://babeljs.io/docs/babel-plugin-transform-typescript

However, this plugin does not add the ability to type-check the JavaScript passed to it. For that, you will need to install and set up TypeScript.

[Johennes]

Neither does babel, it relies on you running tsc yourself.

Oh, I see. Thanks, I've struck out that bullet in the description.