fix!: Rename runner to webExt

[aklinker1]

BREAKING CHANGES:

• Rename ExtensionRunnerConfig type to WebExtConfig

  -import type { ExtensionRunnerConfig } from 'wxt';
  +import type { WebExtConfig } from 'wxt';

Non-breaking deprecations (you'll see a warning if you haven't migrated):

• Deprecate InlineConfig#runner in favor of InlineConfig#webExt

  // wxt.config.ts
  export default defineConfig({
  - runner: {
  + webExt: {
      startUrls: ["https://wxt.dev"],
    }, 
  });

• Deprecate defineRunnerConfig in favor of defineWebExtConfig

  -import { defineRunnerConfig } from 'wxt';
  +import { defineWebExtConfig } from 'wxt';

---

This improves the consistency of naming between the filename (web-ext.config.ts) and the config (WebExtConfig, InlineConfig#webExt). It also provides a bit more clarity that web-ext isn't apart of WXT.

[aklinker1]

Gonna hold off on doing this until we actually create a replacement for web-ext.

[aklinker1]

Nevermind, I want to rename the stuff before 1.0, so reopening.

[codecov]

Codecov Report

Attention: Patch coverage is 42.10526% with 11 lines in your changes missing coverage. Please review.

Project coverage is 81.60%. Comparing base (7c693e8) to head (f69d976).
Report is 1 commits behind head on 0.20.0-breaking-changes.

Files with missing lines	Patch %	Lines
packages/wxt/src/core/define-web-ext-config.ts	30.00%	7 Missing ⚠️
packages/wxt/src/core/resolve-config.ts	50.00%	4 Missing ⚠️

Additional details and impacted files

@@                     Coverage Diff                     @@
##           0.20.0-breaking-changes    #1180      +/-   ##
===========================================================
+ Coverage                    81.16%   81.60%   +0.44%     
===========================================================
  Files                          124      124              
  Lines                         6519     6529      +10     
  Branches                      1088     1098      +10     
===========================================================
+ Hits                          5291     5328      +37     
+ Misses                        1211     1184      -27     
  Partials                        17       17              

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