feat(ci): Add README.md to contracts and fix helm package contract (#733)

Signed-off-by: Javier Rodriguez <[email protected]>

Author: javirln

.github/workflows/contracts/README.md

@@ -0,0 +1,22 @@
+## Chainloop contracts
+
+In this folder all contracts of Chainloop repository are kept as a reference and are the source of truth.
+
+On every push to the `main` branch of the repository, all files contained in `.github/workflows/contracts`
+are updated regardless if they have changed or not. No worries, Chainloop can detect if the file has changed or not
+and update the revision accordingly.
+
+Additionally, the contracts are being updated every day at midnight UTC.
+
+All logic is behind handled by the GitHub action `.github/workflows/sync_contracts.yml`.
+
+### Important note
+The name of the files in `.github/workflows/contracts` should be the same as the contract name since
+it's used for its update. Example:
+- Contract name: `chainloop-deploy`
+- File name: `chainloop-deploy.yml`
+
+Generated update command:
+```bash
+$ chainloop wf contract update --name chainloop-deploy --contract .github/workflows/contracts/chainloop-deploy.yml
+```