docs: fix doxygen (#578)

* chore: ignore docs/doxyxml

* docs: update the README of doxygen

* docs: fix the warnings

* docs: remove the unnecessary step in macOS

* chore: address the review comment

docs/.gitignore

@@ -1 +1,2 @@
 _build
+doxyxml

docs/README.md

@@ -3,20 +3,10 @@
 zenoh-c API documentation is available on [Read the Docs](https://zenoh-c.readthedocs.io/en/latest/index.html).
 
 -------------------------------
-## How to build it 
+## How to build it
 
-  -- Ubuntu -- 
-
-  ```bash
-  $ cd docs
-  $ sphinx-build -b html . _build/html
-  ```
-
-  -- MacOS -- 
-
-  Update conf.py *Config.set_library_file* with the path to your *libclang.dylib* file.
-
-  ```bash
-  $ cd docs
-  $ sphinx-build -b html . _build/html
-  ```
+```bash
+cd docs
+doxygen
+sphinx-build -b html . _build/html
+```

docs/api.rst

@@ -77,7 +77,7 @@ Functions
 .. doxygenfunction:: z_string_is_empty
 
 String Array
------------
+------------
 Types
 ^^^^^
 .. doxygenstruct:: z_owned_string_array_t
@@ -233,9 +233,6 @@ Functions
 .. doxygenfunction:: z_encoding_loan_mut
 .. doxygenfunction:: z_encoding_check
 .. doxygenfunction:: z_encoding_drop
-
-.. doxygenfunction:: z_encoding_drop
-
 .. doxygenfunction:: z_encoding_loan_default
 .. doxygenfunction:: z_encoding_from_str
 .. doxygenfunction:: z_encoding_from_substr
@@ -313,7 +310,7 @@ Predefined Encodings
 .. doxygenfunction:: z_encoding_video_vp9
 
 Reply Error
------
+-----------
 Types
 ^^^^^
 .. doxygenstruct:: z_loaned_reply_err_t
@@ -629,7 +626,7 @@ Functions
 .. doxygenfunction:: z_ring_handler_sample_drop
 .. doxygenfunction:: z_ring_handler_sample_loan
 .. doxygenfunction:: z_ring_handler_sample_recv
-.. doxygenfunction:: z_ring_handler_sample_try_recv  
+.. doxygenfunction:: z_ring_handler_sample_try_recv
 
 Queryable
 =========
@@ -705,7 +702,7 @@ Functions
 .. doxygenfunction:: z_ring_handler_query_drop
 .. doxygenfunction:: z_ring_handler_query_loan
 .. doxygenfunction:: z_ring_handler_query_recv
-.. doxygenfunction:: z_ring_handler_query_try_recv  
+.. doxygenfunction:: z_ring_handler_query_try_recv
 
 Query
 =====
@@ -770,7 +767,7 @@ Functions
 .. doxygenfunction:: z_ring_handler_reply_drop
 .. doxygenfunction:: z_ring_handler_reply_loan
 .. doxygenfunction:: z_ring_handler_reply_recv
-.. doxygenfunction:: z_ring_handler_reply_try_recv  
+.. doxygenfunction:: z_ring_handler_reply_try_recv
 
 Scouting
 ========
@@ -792,8 +789,8 @@ Functions
 .. doxygenfunction:: z_hello_locators
 .. doxygenfunction:: z_hello_zid
 .. doxygenfunction:: z_hello_loan
-.. doxygenfunction:: z_hello_drop 
-.. doxygenfunction:: z_hello_null 
+.. doxygenfunction:: z_hello_drop
+.. doxygenfunction:: z_hello_null
 .. doxygenfunction:: z_hello_check
 
 .. doxygenfunction:: z_whatami_to_view_string