Correct absolute paths in .gitignore to allow for multi-part project

.gitignore

@@ -1,8 +1,8 @@
 # See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
 
 # dependencies
-/node_modules
-/.pnp
+/frontend/node_modules
+/frontend/.pnp
 .pnp.js
 
 # testing
@@ -145,7 +145,7 @@ venv.bak/
 .ropeproject
 
 # mkdocs documentation
-/site
+/c19-backend/site
 
 # mypy
 .mypy_cache/