fix: allowing fixing broken brackets

[Peeeaje]

resolve #1

In main branch, fixing broken brackets by inserting a bracket is impossible.

before

(def x |+ 1 2))
;; inserting `(` at the `|`
(def x ()+ 1 2))

after fix

(def x |+ 1 2))
;; inserting `(` at the `|`
(def x (+ 1 2))

this fix works both for fixing opening brackets and closing brackets.