feat: C509 lib CLI example

[bkioshn]

Description

Implement C509 lib CLI and example

Related Issue(s)

Closes #616

Description of Changes

CLI

• generate command where it generate C509 certificate where it take a JSON file that contains necessary information to create the certificate. If the private key is provided, the certificate is signed.
• verify command where it verify the C509 signature
• decode command where it decode a C509 back to editable and readable file, in this case, JSON format is chosen. If the output is not given, the JSON will only be print out.
• Provide a sample JSON file use to generate C509

Other

• Add PEM file handling in signing.rs
• Add additional necessary functions.

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 102/102}$ | ${\color{red}Fail: 0/102}$ |

[Mr-Leshiy]

LGTM