chore(devcontainer): add WakaTime extension

- Adds the WakaTime extension to the devcontainer JSON file
- Enhances productivity tracking for developers

.devcontainer/devcontainer.json

@@ -12,7 +12,8 @@
     "vscode": {
       "extensions": [
         "/home/xilinx/vsxirepo/vhdl-by-hgb.vsix",
-        "eamodio.gitlens"
+        "eamodio.gitlens",
+        "WakaTime.vscode-wakatime"
       ],
       "settings": {
         "terminal.integrated.defaultProfile.linux": "bash"