Add the extension icon and a command-palette GIF.

The VSIX icon is a 128px branch mark. The README GIF shows wg sb, wg pa, wg fa, and wg st.

Co-authored-by: Tuğrul Alpdoğan <tugrul@alpdogan.co>

Check out the repo before publishing the GitHub release.

gh release create needs a git checkout, so the tag job failed before it could attach the VSIX.

Co-authored-by: Tuğrul Alpdoğan <tugrul@alpdogan.co>