fix: convert cf-kv and excalidraw-libraries from submodules to regular files

- Remove stale cloudflare-worker submodule entry from .gitmodules
- Remove .git dirs from cf-kv and excalidraw-libraries so Git tracks them as regular files
- Fixes 'No url found for submodule path cf-kv' CI error

excalidraw-libraries/stats/2020-12/2020-12-19.json

@@ -0,0 +1,12 @@
+{
+  "dbssticky-data-viz": 53,
+  "g-script-android": 2,
+  "g-script-charts": 9,
+  "g-script-forms": 20,
+  "g-script-medias": 4,
+  "lipis-polygons": 10,
+  "lipis-stars": 7,
+  "morgemoensch-gadgets": 2,
+  "revolunet-raspberrypi3": 4,
+  "youritjang-stick-figures": 21
+}