* Simplifies ETag logic into Source, making if-match conditional requests possible.
* Avoid if-match in FetchSource for latency reasons - use cache buster on ETag change
* handle weak ETags correctly
* add mock fetch server for testing ETags [#90]
* Typing improvements [#287]
* rename FileApiSource to FileSource
* In a few cases we need to use any and biome-ignore. Deferring any restructuring here to js v4.
* replace prettier with biome
* Some HTTP servers will return 206 Partial Content with an ETag for the contents, not the entire resource.
* This change allows the client to continue with mismatched ETags if this case is detected.
