Add launch config to update unit test fixtures (cursorless-dev#1956)

- Extracted from cursorless-dev#1815

## Checklist

- [-] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [-] 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)
- [-] I have not broken the cheatsheet

Author: pokey

.vscode/launch.json

@@ -156,6 +156,23 @@
         "!**/node_modules/**"
       ]
     },
+    {
+      "name": "Update fixtures, unit tests only",
+      "type": "node",
+      "request": "launch",
+      "program": "${workspaceFolder}/packages/test-harness/out/scripts/runUnitTestsOnly",
+      "env": {
+        "CURSORLESS_TEST": "true",
+        "CURSORLESS_TEST_UPDATE_FIXTURES": "true",
+        "CURSORLESS_REPO_ROOT": "${workspaceFolder}"
+      },
+      "outFiles": ["${workspaceFolder}/**/out/**/*.js"],
+      "preLaunchTask": "${defaultBuildTask}",
+      "resolveSourceMapLocations": [
+        "${workspaceFolder}/**",
+        "!**/node_modules/**"
+      ]
+    },
     {
       "name": "Docusaurus start",
       "type": "node",