Make it easier to have unit tests in VSCode packages (#1541)

Introduces a new convention for tests that end with `.vscode.test.ts`
must run within VSCode; other tests can be run as unit tests outside of
VSCode. This makes it easier to add unit tests within packages such as
`cursorless-vscode`. Just because a package is designed to be used with
VSCode doesn't mean that all of its tests should have to be run within a
VSCode context. It might (and should!) have support code that consists
of pure functions with no dependencies.

- Required by #1523 

## Checklist

- [x] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [x] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [x] I have not broken the cheatsheet

Author: pokey

docs/contributing/CONTRIBUTING.md

@@ -76,6 +76,8 @@ Run the `workbench.action.debug.selectandstart` command and then select
 
 See [test-case-recorder.md](./test-case-recorder.md).
 
+It is also possible to write manual tests. When doing so, we have a convention that any test that must be run within a VSCode context (eg because it imports `"vscode"`), should be placed in a file with the suffix `.vscode.test.ts`. All other tests should end with just `.test.ts`. This allows us to run non-VSCode tests locally outside of VSCode using the `Run unit tests` launch config. These tests run much faster than the full VSCode test suite.
+
 ## Parse tree support
 
 ### Adding a new programming language