[54] support bi-directional filesystem conventions

[TomStrepsil]

Issue

resolves #54
enables #46

Details

Change the webpack package so that rather than using import.meta.webpackContext to create a context module, hand-roll an equivalent data structure (mapping paths to statically-imported modules), and perform the same chaining of module splits as is afforded by this API (i.e. cascade context targets that themselves have a contextual split).

Rather than the bespoke require.context data structure, a simpler Map is produced by the join point generator, passing it to the point cut as variantPathMap (from variants), which in turn passes it to the toggle handler. This represents a breaking change for consumers that have used a bespoke toggle handler.

Scout Rule

webpack package

• remove NextJs peer dependency, there's no reason to be explicit
• ensured unresolvable files (can happen if node_modules part of the app root, and something odd has happened) are skipped
• refactored the webpackNormalModule option to just take a module, rather than an async function - born out of a mistake when importing originally, I assume
• consolidated defaulting of options to single method, rather than separating point cut defaults from plugin core defaults, for simplicity
• ensured circular references don't cause the module graph walk to lock up
• let enhanced-resolve attempt resolution in a try/catch, to support module alias etc.
• fixed documentation to indicate toggleHandler is an option of the pointCut, not general plugin configuration

repo root / examples

• updated eslint-plugin-workspaces to 0.11.0 after addition of ESLint9 support

express example

• removed "Vary" header from "animals" example, the page is meant to be un-cacheable, and the value was wrong in any case

all examples

• moved to import typescript types explicitly (as type) after unexpected pipeline failure

Upgrade Guide

• If a bespoke toggleHandler has been specified in the Webpack plugin, this should be updated to take a variantPathMap argument (which is a Map) in place of a variants argument which was a require.context module.

See changes to examples/serve/src/toggleHandlers in this PR for reference.

• If a webpackNormalModule has been supplied, this should now return an imported module itself, rather than an resolution function

CheckList

• PR starts with [ISSUE_ID].
• Has been tested (where required) before merge to main.