Add PocketPay Contracts meaningful change threshold guide

[El-swaggerito]

Description

Difficulty: Hard

Type: Documentation

Summary

Create a meaningful change threshold guide for PocketPay Contracts PRs.

Current Behaviour

Some PRs may only include very small code changes without solving the underlying issue.

Expected Behaviour

The repo should explain that line count alone is not the standard, but the change must be complete, tested, and aligned with the issue requirements.

Suggested Implementation

Document examples of meaningful changes, insufficient changes, and how reviewers should assess scope.

Files or Areas Likely Affected

• contracts/
• src/
• tests/
• docs/
• README.md
• Makefile

Acceptance Criteria

• Meaningful change threshold guide is added.
• Guide explains that line count alone is not the only measure.
• Small but complete changes are distinguished from small incomplete changes.
• Insufficient examples are included.
• Reviewer assessment guidance is included.
• README links to the guide.

Additional Notes

This responds to concerns about very small merged PRs.

[CleanDev-Fix]

Hi, I would like to work on this.

My planned approach:

1. Add a focused meaningful-change guide that evaluates outcomes and evidence rather than line count alone.
2. Distinguish small complete changes from small incomplete changes with contract and documentation examples, then give reviewers a short assessment flow.
3. Link the guide from the README and the existing contribution quality gate, and verify the Markdown links and required guidance.

One boundary I will keep in mind: I will build on the existing quality gate instead of duplicating it, and keep this documentation-only with no contract behavior changes.

Does this approach line up with what you want for this issue?