Added Talon notification if the user has cloned the monorepo (#2690)

Related ##1953

## 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

---------

Co-authored-by: Pokey Rule <[email protected]>
Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

dont_clone_monorepo.py

@@ -0,0 +1,17 @@
+"""
+This file exists in our monorepo so that if someone accidentally clones this monorepo
+into their talon folder instead of cursorless-talon, they'll get a helpful error popup
+"""
+
+from talon import app
+
+
+def on_ready():
+    app.notify(
+        "Whoops! You cloned our monorepo instead of cursorless-talon",
+        "Please remove cursorless and clone cursorless-talon instead:",
+        "https://github.com/cursorless-dev/cursorless-talon",
+    )
+
+
+app.register("ready", on_ready)