chore: add contributing docs, rename folder to schema

CONTRIBUTING.md

@@ -0,0 +1,31 @@
+# Contributing
+
+Thank you for your interest in contributing to the Profilarr Schema! This schema
+serves as the foundation for all Profilarr Compliant Databases, so stability and
+careful consideration of changes is critical.
+
+## Before Contributing
+
+**ALL contributions must be discussed before submitting a pull request.** This
+is not negotiable. The schema affects every PCD and Profilarr installation, so
+changes have far-reaching consequences.
+
+### Discussion Channels
+
+Please use one of the following channels to propose changes:
+
+- **Discord**: [Join our Discord server](https://discord.gg/XGdTJP5G8a) for
+  real-time discussion
+- **GitHub Issues**:
+  [Open an issue](https://github.com/Dictionarry-Hub/schema/issues) for
+  structured proposals
+
+### What to Include in Your Proposal
+
+When proposing a change, please provide:
+
+1. **The problem**: What limitation or issue does this address?
+2. **The solution**: What specific schema change are you proposing?
+3. **Impact analysis**: How does this affect existing PCDs and Profilarr
+   installations?
+4. **Migration path**: How would existing databases adapt to this change?