Add installing vscode extensions automatically

Currently, a list of installed extensions is in `vscode_manual`. It can be backed up using

```bash
code --list-extensions > vscode_manual/extensions.txt
```

And they can be installed using:
```bash
cat extensions.txt | xargs -L 1 code --install-extension
```

Add this to `uinstall.sh` or `install.py` or something.