Add support for arbitrary module namespace identifiers

[lukastaegert]

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:

• resolves ES2022: arbitrary module namespace names #4322

Description

This adds support for ES2022 arbitrary module namespace identifiers, i.e.

import { '=>' as foo } from './foo.js';
export { foo as '=>' };
export { '=>' as '<=' } from './foo.js';

[github-actions]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#gh-4322-arbitrary-module-namespace-identifiers

or load it into the REPL:
https://rollupjs.org/repl/?pr=4770

[codecov]

Codecov Report

Merging #4770 (b9566a0) into master (57fa7e0) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4770      +/-   ##
==========================================
- Coverage   99.03%   99.03%   -0.01%     
==========================================
  Files         217      217              
  Lines        7774     7773       -1     
  Branches     2154     2159       +5     
==========================================
- Hits         7699     7698       -1     
  Misses         24       24              
  Partials       51       51              

Impacted Files	Coverage Δ
src/Module.ts	100.00% <100.00%> (ø)
src/ast/nodes/NodeType.ts	100.00% <0.00%> (ø)

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[rollup-bot]

This PR has been released as part of rollup@3.9.0. You can test it via npm install rollup.