[build] create a PR for vendorized unzip_http.py when dispatch received

[anjakefala]

Uses: https://github.com/marketplace/actions/create-pull-request and https://github.com/peter-evans/repository-dispatch.

Relies on https://github.com/saulpw/unzip-http/pull/11. We would need to create an ACCESS_KEY, I believe. We would also need to turn on github actions for VisiData.

Untested!