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)

test/src/unit-cbor.cpp

@@ -1287,7 +1287,7 @@ TEST_CASE("CBOR")
         }
     }
 
-    SECTION("additonal deserialization")
+    SECTION("additional deserialization")
     {
         SECTION("0x7b (string)")
         {