The docs for provideFileSearchResults should provide guidance how to interpret pattern

[jrieken]

Testing #226668

Today, the docs just say "The search pattern to match against file paths." This leaves a lot of room for speculation and it's not clear if matching is substring, startWith, case-sensitive, fuzzy etc.

For the WorkspaceSymbolProvider api we have very similar challenge and with it we are very explicit how the search string should be interpreted:

vscode/src/vscode-dts/vscode.d.ts

Lines 3599 to 3602 in 7473068

	* The `query`-parameter should be interpreted in a *relaxed way* as the editor will apply its own highlighting
	* and scoring on the results. A good rule of thumb is to match case-insensitive and to simply check that the
	* characters of *query* appear in their order in a candidate symbol. Don't use prefix, substring, or similar
	* strict matching.