Merge branch 'dev'
Bump up version to 0.9.1
See if pattern is empty for stay command
doc: Fix grammar & highlight group document
doc: Fix grammatical error in the README
Revert "doc: Fix grammatical error in the README"

Because this commit contained unexpected contents

This reverts commit 7e04dad80e385b12c2d0089b9c1a9af221e8feeb.
doc: Fix grammatical error in the README