fix(html): prepare for Rollup 3

[lukastaegert]

BREAKING CHANGES: Requires Node 14

Rollup Plugin Name: html

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) Requires Node 14
• no

If yes, then include "BREAKING CHANGES:" in the first commit message body, followed by a description of what is breaking.

List any relevant issue numbers:

Description

This PR updates the plugin for Rollup 3 compatibility. This will not change compatibility with older Rollup versions.

• It should be merged after chore(repo): central changes for Rollup 3 updates #1277

It contains the following:

• Update minimal required Node version to 14 (also reflected in README, breaking change)
• Extend Rollup peerDependency version with ||^3.0.0
• Make Rollup an optional peerDependency as technically, plugins do not require Rollup but only depend on its API. Apparently solves issues with pnpm, see fix(inject): rollup is optional peer dependency #1272
• Use a shared Rollup config for all plugins

  • This allows to share bundling improvements and unifies the build

  • All plugins now use strictDeprecations to fail early if they use deprecated Rollup features as well as an onward handler that fails the build

  • The CJS output now uses

    exports: 'named',
    footer: 'module.exports = Object.assign(exports.default, exports);'
    

    which will allow the default export to be directly required while still supporting named exports

• The "exports" package.json field is now properly configured for require and import.
• CJS and ESM output are now in different sub-folders with a package.json file with "type": "module" next to the CJS output (via the shared Rollup config)
• Internally, the latest Rollup 3 pre-release build is used to ensure compatibility
• Rollup configs now follow Node semantics, i.e. .mjs for ESM configs, no direct import of package.json
• TypeScript output has been changed to target ES2019