fix(secret): use .eyJ keyword for JWT secret

[DmitriyLewen]

Description

use .eyJ keyword for JWT secret

Related issues

• Close JWT secret detector only works if "JWT" word is in scope #6802

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[knqyf263]

I think .eyJ is better.

1. JWT headers typically start with {".
2. ASCII codes:
   • {: 123 (01111011 in binary)
   • ": 34 (00100010 in binary)
3. Combining these: 011110110010001
4. Grouping into 6-bit segments: 011110 | 110010 | 0010xx
5. Decimal values: 30 | 50 | ?
6. Base64 encoded: e | y | ?
7. The next character is often 'J' because:
   • The third character in the JWT header is usually the start of a key (e.g., "alg" or "typ").
   • All a-zA-Z characters start with '01' in binary.
   • When grouped with the previous bits: 011110 | 110010 | 001001
   • The third group (001001) is 9 in decimal, which corresponds to 'J' in Base64.

Therefore, JWTs typically start with "eyJ". The second body also starts with eyJ, leading to .eyJ in the entire payload.

[DmitriyLewen]

Wow, nice logical chain 👍
I updated keywords in 1e6a54a