build: update WinGet publish workflow to use env instead of --token (#…

…467)

With the latest winget-create release, the preferred method for
providing the GitHub token in CI/CD environment is via the environment
variable `WINGET_CREATE_GITHUB_TOKEN`. Removed use of `--token` and
switched to environment variable. See https://aka.ms/winget-create-token
for details.

Add CI action for publishing package to WinGet (#189)

This is similar to the one in microsoft/terminal,
and uses wingetcreate.

Fix clearing of editlines (#31)

This only became apparent now that the
Open dialog clears the filename field.