[docs] Refactor & update API documentation

mkdocs.yml

@@ -24,9 +24,10 @@ plugins:
       projects:
         # project names must be alphanumeric, else snippets won't work
         ltapi:
-          src-dirs: arduino/libretuya/
+          src-dirs: cores/common/
           doxy-cfg:
-            PREDEFINED: __cplusplus
+            OPTIMIZE_OUTPUT_FOR_C: YES
+            PREDEFINED: __cplusplus DOXYGEN=1
             CASE_SENSE_NAMES: NO
       save-api: .
   - literate-nav:
@@ -34,11 +35,6 @@ plugins:
   - section-index
   - include-markdown
   - search
-  - git-revision-date-localized:
-      type: timeago
-      enable_creation_date: true
-      exclude:
-        - ltapi/*
 
 extra_css:
   - docs/style.css