refactor: prepare for external typescript support

[kevinmarrec]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Refactor some internals so it can fits to the outsourcing/externalization of the typescript support.

1. Ability to make modules extend Builder supportedExtensions + refactor of createRoutes function signature to fit better and pass these supported extensions.

2. Ability to make modules customize Webpack WarningFix plugin filters.

3. Ability to make modules grab the Nuxt babelLoader (with our predefined babel options) to use it when extending webpack config. Useful to use it with in typescript module with ts-loader to handle tsx files.

Related : #5858

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-io]

Codecov Report

Merging #5854 into dev will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev    #5854      +/-   ##
==========================================
- Coverage   95.72%   95.68%   -0.04%     
==========================================
  Files          82       82              
  Lines        2690     2689       -1     
  Branches      690      690              
==========================================
- Hits         2575     2573       -2     
- Misses         97       98       +1     
  Partials       18       18

Flag	Coverage Δ
#e2e	100% <ø> (ø)	⬆️
#fixtures	50.35% <100%> (-0.02%)	⬇️
#unit	92.67% <100%> (-0.04%)	⬇️

Impacted Files	Coverage Δ
packages/config/src/config/build.js	100% <ø> (ø)	⬆️
packages/webpack/src/plugins/warning-ignore.js	100% <ø> (ø)
packages/utils/src/route.js	100% <100%> (ø)	⬆️
packages/webpack/src/config/base.js	94.94% <100%> (ø)	⬆️
packages/builder/src/builder.js	99.6% <100%> (ø)	⬆️
packages/vue-renderer/src/renderer.js	93.49% <0%> (-0.82%)	⬇️

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[kevinmarrec]

@pi0 Should we rename https://github.com/nuxt/nuxt.js/blob/dev/packages/webpack/src/plugins/warnfix.js#L12 too ?
warnignore.js / warning-ignore.js ?

[pi0]

@kevinmarrec yes, please. seems a more reasonable name now

[kevinmarrec]

PR should be fine now, i'm not sure if it's relevant adding documentation for build.warningIgnoreFilters & build.additionalExtensions as it's things that users won't customize at all.

[pi0]

LGTM

[Atinux]

LGTM