Explicitly set $GIT_SEQUENCE_EDITOR when launching from cli `github .`

### The problem

rebase stuff pops open my `$GIT_SEQUENCE_EDITOR` (vscode)

### Release version

Version 3.1.1 (arm64)

### Operating system

macOS 12.6

### Steps to reproduce the behavior

_No response_

### Log files

_No response_

### Screenshots

_No response_

### Additional context

`github .` should override `$GIT_SEQUENCE_EDITOR` to point to itself.