Fix some spelling errors - mostly in comments & documentation.

I did not touch the Changelog file and any third party stuff.

additonal -> additional (1)
apppend -> append (2)
constuctor -> constructor (2)
contect -> context (2)
dobulequote -> doublequote (1)
elemnts -> elements (1)
exakt -> exact (2)
exluded -> exclude (1)
explicitely -> explicitly (2)
narcissic -> narcissistic (1)
ocurred -> occurred (1)
occuring -> occurring (2)
preceeds -> preceded (1)
ot -> to (2)
wehther -> whether (2)

include/nlohmann/detail/input/binary_reader.hpp

@@ -1929,7 +1929,7 @@ class binary_reader
     /*!
     @param[in] format   the current format
     @param[in] detail   a detailed error message
-    @param[in] context  further contect information
+    @param[in] context  further context information
     @return a message string to use in the parse_error exceptions
     */
     std::string exception_message(const input_format_t format,