CMake cleanup (#2885)

* 🔥 clean CMake files and Makefile
* 💡 update documentation

doc/mkdocs/docs/features/parsing/parse_exceptions.md

@@ -1,4 +1,4 @@
-# Parsing and exceptions
+# Parsing and Exceptions
 
 When the input is not valid JSON, an exception of type [`parse_error`](../../home/exceptions.md#parse-errors) is thrown. This exception contains the position in the input where the error occurred, together with a diagnostic message and the last read input token. The exceptions page contains a [list of examples for parse error exceptions](../../home/exceptions.md#parse-errors). In case you process untrusted input, always enclose your code with a `#!cpp try`/`#!cpp catch` block, like