feat!: Remove webextension-polyfill

[aklinker1]

This is not being merged into main, but the v0.20.0 staging branch.

---

BREAKING CHANGE: WXT no longer uses the webextension-polyfill because it doesn't provide any value anymore. As long as you're not developing a legacy MV2 extension for Chrome, nothing changes about how you're importing and using WXT's browser at runtime - your extension should behave the exact same way!

However, there are a few changes you might need to make to your non-runtime code:

• If you use TypeScript, extension API types are now apart of the browser variable, not separate imports:

  - import { type Runtime} from 'wxt/browser';
  + import { browser } from 'wxt/browser';
  
  - function getSenderId(sender: Runtime.Sender) { 
  + function getSenderId(sender: browser.runtime.Sender) { 

• If you set extensionApi option in your wxt.config.ts, remove it:

  export default defineConfig({
  - extnsionApi: "chrome",
  });

• If you disabled auto-imports and were importing from wxt/browser/chrome, you can go back to importing from wxt/browser:

  - import { browser } from 'wxt/browser/chrome';
  + import { browser } from 'wxt/browser';

To continue using the polyfill, install the NPM package and import it instead of using wxt/browser:

pnpm i webextension-polyfill
pnpm i -D @types/webextension-polyfill

import browser from 'webextension-polyfill';

console.log(browser.runtime.id);

[codecov]

Codecov Report

Attention: Patch coverage is 94.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 81.66%. Comparing base (842c158) to head (615f68a).
Report is 2 commits behind head on 0.20.0-breaking-changes.

Files with missing lines	Patch %	Lines
...src/core/builders/vite/plugins/extensionApiMock.ts	0.00%	1 Missing ⚠️
packages/wxt/src/core/utils/content-scripts.ts	66.66%	1 Missing ⚠️
...es/wxt/src/virtual/utils/reload-content-scripts.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                     Coverage Diff                     @@
##           0.20.0-breaking-changes    #1084      +/-   ##
===========================================================
- Coverage                    82.07%   81.66%   -0.42%     
===========================================================
  Files                          127      125       -2     
  Lines                         6661     6625      -36     
  Branches                      1112     1107       -5     
===========================================================
- Hits                          5467     5410      -57     
- Misses                        1180     1198      +18     
- Partials                        14       17       +3     

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