Bug 1686678 - Prepare Glean.js for publishing

[brizental]

This is on top of #72. As such, it is blocked until that PR is merged (or not merged).

Dry run logs for reference:

> @mozilla/glean@0.1.0 prepare .
> npm run build


> @mozilla/glean@0.1.0 build /Users/beatrizmachado/Documents/work/glean.js/glean
> webpack --config webpack.config.js --mode production

asset qt.js 54.7 KiB [emitted] [minimized] (name: main)
orphan modules 18.7 KiB [orphan] 14 modules
runtime modules 670 bytes 3 modules
modules by path ./src/ 87.9 KiB
  modules by path ./src/core/ 84 KiB 24 modules
  modules by path ./src/platform/ 2.39 KiB
    ./src/platform/qt/index.ts 408 bytes [built] [code generated]
    ./src/platform/test/index.ts 1010 bytes [built] [code generated]
    ./src/platform/test/storage.ts 1.01 KiB [built] [code generated]
  ./src/index.ts 1.42 KiB [built] [code generated]
./node_modules/uuid/dist/esm-browser/index.js + 14 modules 19.1 KiB [built] [code generated]
./package.json 1.96 KiB [built] [code generated]
webpack 5.21.2 compiled successfully in 5858 ms

asset webext.js 58.9 KiB [emitted] [minimized] (name: main)
orphan modules 18.7 KiB [orphan] 14 modules
runtime modules 670 bytes 3 modules
modules by path ./src/ 96.2 KiB
  modules by path ./src/core/ 84 KiB 24 modules
  modules by path ./src/platform/ 10.8 KiB
    modules by path ./src/platform/webext/*.ts 8.76 KiB 4 modules
    modules by path ./src/platform/test/*.ts 2 KiB
      ./src/platform/test/index.ts 1010 bytes [built] [code generated]
      ./src/platform/test/storage.ts 1.01 KiB [built] [code generated]
  ./src/index.ts 1.42 KiB [built] [code generated]
./node_modules/uuid/dist/esm-browser/index.js + 14 modules 19.1 KiB [built] [code generated]
./package.json 1.96 KiB [built] [code generated]
webpack 5.21.2 compiled successfully in 5957 ms
npm notice 
npm notice 📦  @mozilla/glean@0.1.0
npm notice === Tarball Contents === 
npm notice 56.0kB dist/qt.js    
npm notice 60.3kB dist/webext.js
npm notice 2.3kB  package.json  
npm notice === Tarball Details === 
npm notice name:          @mozilla/glean                          
npm notice version:       0.1.0                                   
npm notice package size:  29.3 kB                                 
npm notice unpacked size: 118.7 kB                                
npm notice shasum:        1ad68d01c7a0d48353f0e2a8bee1a11ccd388217
npm notice integrity:     sha512-qYQZX+KZPIt7n[...]99dYsLrbe+R1g==
npm notice total files:   3                                       
npm notice 
+ @mozilla/glean@0.1.0

[Dexterp37]

r+