feat/schema: add ast and test

schema/main.go

@@ -1,2 +1,18 @@
 //go:generate gocc -a azschema.bnf
 package schema
+
+import (
+	"azalea/schema/ast"
+	"azalea/schema/lexer"
+	"azalea/schema/parser"
+)
+
+func CreateSchema(in string) (schema ast.Schema, err error) {
+	s := lexer.NewLexer([]byte(in))
+	p := parser.NewParser()
+	a, err := p.Parse(s)
+	if err == nil {
+		schema = ast.Schema(a.(ast.ExprList))
+	}
+	return
+}