RFC: Elaborating Github project description

[pfalcon]

Current Github description for this project is "FreeRTOS PSA PKCS11". That's too terse and clearly misses descriptive words to convey what it is. Colloquially it is referred as "shim" (e.g. in the current README), but that word is pretty much a developer slang, and in all fairness, with 100K+ source code, it's not really a shim. More formal word for what it does is "adapter" (as in "API adapter"), but for security-related things, there's even better established term - "security provider". That's as an alternative to something like "security driver", because term "driver" has strong connotation of being related to hardware.

With the above in mind, I propose to change the Github description "FreeRTOS PKCS11 security provider for PSA/TrustedFirmware-M". If the change goes thru, then apparently also update other references too.

One thing I'm not sure is how "security provider" term is established in FreeRTOS landscape (for example, maybe it's used for slightly different meaning).

Let me know if you agree/disagee. Thanks.