* Implemented `-d`/`--diff` flag to print unified diffs.
* Added `unifiedDiff` function for generating diffs.
* Config discovery now merges fields from `.pgtidy.yaml`.
* Implemented formatting for BEGIN...END blocks in PL/pgSQL.
* Added logic to handle indentation and blank lines.
* Introduced tests for broken formatting cases.
* add formatBody and formatBodyInner functions for DECLARE section
* update needSpace to handle LBracket correctly
* enhance semanticallyEqual to compare dollar-quoted bodies
* add test data for broken layout scenarios