Add certificate examples

[seanturner]

Add certificate examples (thanks Bas).

[seanturner]

@danvangeest could I impose on you to save me a lot of time and provide me with the dumpasn1 output to include in the 3 places for the pretty print?

[danvangeest]

Attaching files because I can't push to this PR directly:

ML-KEM-512.crt.txt
ML-KEM-768.crt.txt
ML-KEM-1024.crt.txt

Also, you could add this to the beginning of the Makefile:
DEPS_FILES :=
example/ML-KEM-1024.crt
example/ML-KEM-1024.priv
example/ML-KEM-512.crt.txt
example/ML-KEM-512.pub
example/ML-KEM-1024.crt.txt
example/ML-KEM-1024.pub
example/ML-KEM-768.crt
example/ML-KEM-768.priv
example/ML-KEM-512.crt
example/ML-KEM-512.priv
example/ML-KEM-768.crt.txt
example/ML-KEM-768.pub

[bwesterb]

Please consider merging #84 into this branch before merging.