Update frontend.md with mouse commands
Update frontend.md with mouse commands

google/xi-editor,google/xi-editor,fuchsia-mirror/third_party-xi-editor,modelorganism/xi-editor,fuchsia-mirror/third_party-xi-editor,modelorganism/xi-editor,google/xi-editor,fuchsia-mirror/third_party-xi-editor,modelorganism/xi-editor,fuchsia-mirror/third_party-xi-editor,google/xi-editor