docs: rename Types page to API

Author: MilesCranmer

docs/src/types.md renamed to docs/src/api.md

@@ -1,4 +1,4 @@
-# Types
+# API
 
 ## Operator Enum
 

docs/src/index.md

@@ -2,5 +2,5 @@
 # Contents
 
 ```@contents
-Pages = ["utils.md", "types.md", "eval.md"]
+Pages = ["utils.md", "api.md", "eval.md"]
 ```