Add Coding Guidelines and Common Vulnerabilities (OWASP Top 10 and Language-specific)

[StefanDziwok]

These are missing activities that are also within the security-by-design topic.

We can use our training for some examples.

[mvollmary]

Enriching the following activities:

• https://github.com/AppSecure-nrw/security-belts/blob/master/yellow/unit-tests-for-security-features.md
• https://github.com/AppSecure-nrw/security-belts/blob/master/orange/regular-security-training-for-everyone.md
• https://github.com/AppSecure-nrw/security-belts/blob/master/yellow/security-code-review.md

[thorsten-koch]

Coding Guidelines Overview.pdf