Update README.md

README.md

@@ -8,4 +8,11 @@ Browse & edit Hypermerge documents. This VSCode extension was built to work with
 * In the File / Documents tab, you should now see a HypermergeFS tab.
 * Hover over the title of that tab, click the [...] icon, select "Open Document" and paste in a hypermerge document link.
 
+If you want to work on, debug, or develop on the VSCode extension follow these steps instead:
+ * Check out this repository.
+ * `npm install` (as of this writing, the repo does not work with yarn because of choices made upstream. patches welcome)
+ * Open the repository in vscode (e.g. `$ code . `)
+ * Go to Debug -> Start Debugging (F5) in the menu.
+ * A second, new VSCode window will open running the extension version you just built. You'll be able to put breakpoints in the code and see debug output in your original window. The new window will be labeled \[Extension Development\] so you can recognize it.
+
 You're off to the races!