Add QCBORDecoder_Tell(); traversal cursor position bug fix (#223)

Adds QCBORDecode_Tell() to return traversal cursor position.

Fixes a traversal cursor position bug. The position was not correct after a QCBORDecode_GetXXXInX() of a non-aggregate item by label (e.g., QCBORDecode_GetInt64InMapN()) in an array that was entered.

Fixes to documentation for traversal cursor.

Addresses #213


* Add QCBORDecoder_Tell()

* Testing near complete and passing

* More tests and documentation

* Add some more documentation

* typo

---------

Co-authored-by: Laurence Lundblade <lgl@securitytheory.com>
diff --git a/src/qcbor_encode.c b/src/qcbor_encode.c
index fa3486e..af83099 100644
--- a/src/qcbor_encode.c
+++ b/src/qcbor_encode.c
@@ -474,7 +474,7 @@
    /* This expression integer-promotes to type int. The code above in
     * function guarantees that nAdditionalInfo will never be larger
     * than 0x1f. The caller may pass in a too-large uMajor type. The
-    * conversion to unint8_t will cause an integer wrap around and
+    * conversion to uint8_t will cause an integer wrap around and
     * incorrect CBOR will be generated, but no security issue will
     * occur.
     */