Internal: Use Esbuild instead of Rollup for compiling a main.js file.

[Taitava]

(This should not affect endusers.)

Useful commits from Obsidian Sample plugin:

1. [ ] Update sample plugin to use ESBuild.
2. [ ] Use ESBuild API instead of passing command line arguments / https://github.com/obsidianmd/obsidian-sample-plugin/pull/16
3. [ ] Update build script to include external node packages.
4. [ ] Update esbuild script to include codemirror packages as external.