also extract attributes source for id-only implicit-div tags

Like in #54, allow linters like Rubocop and SpaceInsideHashAttributes to inspect hash attributes for implicit-div tags that also have no static class, but just a static id (e.g. `#my_id{ foo: 'bar' }`).

Is there a reason we have the `%` separated from the character class containing `.` and `#`? Seems like we could combine them all into one class as they are all valid leading characters.