Allow for backspace through the end parenthesis to succeed

[Jay-Madden]

Right now you can backspace starting from the right side of the close parenthesis.

The plugin should detect this attempt and instead pass the cursor through to the other side to begin editing inside the parenthesis instead of appearing to do to nothing

Example:

                       <Cursor>
func Foo() (int, error)| {

}

When backspace is hit the cursor will seem to not move and stay in one place because the plugin will idempotently recreate the parenthesis from the new parse.

We should instead move the cursor to the left one block to simulate backspacing THROUGH the ) and into the content itself where you can do whatever you want.