extmods: Moved documentation under FAQs

Author: jpeletier

mkdocs.yml

@@ -29,10 +29,10 @@ pages:
 - FAQs:
     - Lua Developer FAQ: 'lua-developer-faq.md'
     - Extension Developer FAQ: 'extn-developer-faq.md'
+    - Writing external C modules: 'modules/extmods.md'
 - Whitepapers:
     - Filesystem on SD card: 'sdcard.md'
 - C Modules:
-    - 'Writing external C modules' 'modules/extmods.md'
     - 'adc':          'modules/adc.md'
     - 'bit':          'modules/bit.md'
     - 'bthci':        'modules/bthci.md'