add cmake example tie in

[JacobBarthelmeh]

ZD14997

[dgarske]

This is super useful! Thanks.

Works as described, but do get a code warning:

[ 98%] Building C object CMakeFiles/hash.dir/myApp.c.o
/Users/davidgarske/GitHub/wolfssl-examples/cmake/myApp.c:40:37: warning: passing 'char *' to parameter of type 'const byte *' (aka 'const unsigned char *') converts between pointers to integer types with different sign [-Wpointer-sign]
        ret = wc_Sha256Update(&sha, argv[1], (word32)XSTRLEN(argv[1]));
                                    ^~~~~~~
/Users/davidgarske/GitHub/wolfssl-examples/cmake/wolfssl/wolfssl/wolfcrypt/sha256.h:242:61: note: passing argument to parameter 'data' here
WOLFSSL_API int wc_Sha256Update(wc_Sha256* sha, const byte* data, word32 len);
                                                            ^
1 warning generated.

[JacobBarthelmeh]

Thanks for the review! Added a cast and Init/Cleanup functions.