Add FAQ entry about pinning to branch of stylelint
Add FAQ entry about pinning to branch of stylelint

Closes #1968

stylelint/stylelint,gucong3000/stylelint,gucong3000/stylelint,hudochenkov/stylelint,stylelint/stylelint,stylelint/stylelint,hudochenkov/stylelint,hudochenkov/stylelint,gucong3000/stylelint,stylelint/stylelint