docs: add example to initialize PIN with pkcs11-tool

[frankmorgner]

fixes #2867

Checklist

• Documentation is added or updated
• New files have a LGPL 2.1 license statement
• PKCS#11 module is tested
• Windows minidriver is tested
• macOS tokend is tested

[frankmorgner]

No, this was not an accident. Note the previous check for type != NULL, which makes any value of kind type + X also non-NULL. All that could happen is that the derived value points to'\0', but strcmp will not match that to a gost parameter set and atol in the RSA/AES case will return 0 so that the subsequent check of the key_length will fail.

As written in the commit message ac77fc8, this disallows the use of default key length. This was implemented for RSA, for example, but the user had to use RSA: (note the colon at the end). As User, I would have wanted a default value only without the colon. Additionally, if the user supplies RSA:abcde, then atol also returns 0, which currently results in the default key length rather than being treated as error. That's why, I changed --key-type to not use any default values.

[Jakuje]

Thank you!