This bundles the extension files using esbuild, as recommended by
VSCode. This reduces the size of the extension from 34MB to less than
5MB.
Gulp will still run TypeScript to check types, but will not use the
TypeScript compiler output in the bundle.
Tests are now run separately, outside of Gulp, so their data doesn't
need to be copied anymore.
See: https://code.visualstudio.com/api/working-with-extensions/bundling-extension
Koen Vlaswinkel
Elena Tanasoiu
Andrew Eisenberg
Jason Reed