feat: Export defineConfig defines the auxiliary function of the configuration

[rxliuli]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers: #4125

Description

[rxliuli]

@lukastaegert I added some documentation at the end

[github-actions]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rxliuli/rollup#feat_defineConfig

or load it into the REPL:
https://rollupjs.org/repl/?pr=4127

[codecov]

Codecov Report

Merging #4127 (555cac3) into master (9f69fe3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4127   +/-   ##
=======================================
  Coverage   98.12%   98.12%           
=======================================
  Files         201      201           
  Lines        7077     7077           
  Branches     2071     2071           
=======================================
  Hits         6944     6944           
  Misses         64       64           
  Partials       69       69           

Impacted Files	Coverage Δ
src/rollup/rollup.ts	100.00% <ø> (ø)

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[lukastaegert]

You should make this a #### sub-heading so that it looks right on the web site

[lukastaegert]

Otherwise looks great!

[rxliuli]

added: 555cac3

[lukastaegert]

Thanks 👍

[rxliuli]

I would like to ask, if yes, is it possible to support ts type configuration files? If I create a new PR to support this feature, will it be merged?

[lukastaegert]

There is already a PR for this which got stalled: #3835
However, discussions were already pretty advanced, maybe we can move that one forward? The general idea would be to allow using plugins to transpile the config file, just the specifics were not finalized.