[backend] add DEVELOPMENT.md

Author: ZenVoich

backend/DEVELOPMENT.md

@@ -0,0 +1,11 @@
+# Development
+
+## Folder structure
+- `main/` - Package registry canister
+- `storage/` - Storage canisters (spawned from `main` canister)
+
+## Guidelines
+- Avoid making breaking changes to the API - this will break the users with older versions of the CLI
+  - Favor implementing new features with deprecating old ones for gradual adoption
+  - If you still need to make a breaking change, update the API version in the `main-canister.mo` file and create a new release
+- Recommended to deploy staging(backend and frontend) first (`dfx deploy --network staging ...`)