feat: add a parser and AST

Author: kiwicopple

README.md

@@ -11,6 +11,9 @@ https://supabase.github.io/postgres-meta/
 Schema:
 
 - [X] `POST /query` (Execute SQL query)
+  - [ ] `POST /format` (Format SQL query)
+  - [ ] `POST /parse` (Parse SQL query into AST)
+  - [ ] `POST /explain` (Explain SQL query)
 - [X] `/columns`
   - [X] GET (List)
   - [X] POST (`alter table add column`)