add deployment-payload docs

Author: GrantBirki

docs/deployment-payload.md

@@ -0,0 +1,19 @@
+# Deployment Payloads
+
+The deployment payload is a JSON data structure that gets uploaded to GitHub when a new deployment is created. The values in this payload can be almost anything you want. The branch-deploy GitHub Action hydrates the deployment payload with some useful information that can be accessed later on in the deployment process if you need it.
+
+Here is the data that the branch-deploy Action will add to the deployment payload:
+
+```json
+{
+    "params": "<string>",
+    "parsed_params": "<object>",
+    "sha": "<string>",
+    "type": "branch-deploy"
+}
+```
+
+- `params` - This is the raw string of parameters that were passed to the branch-deploy Action. You can read more about parameters [here](./parameters.md).
+- `parsed_params` - This is the parsed version of the `params` string. This is a JSON object that is created by parsing the `params` string. You can read more about parameters [here](./parameters.md).
+- `sha` - This is the commit SHA that is being deployed.
+- `type` - This is the type of deployment that is being created. This will always be `branch-deploy` for the branch-deploy Action.

docs/parameters.md

@@ -75,3 +75,7 @@ The `params` and `parsed_params` outputs can be accessed just like any other out
     echo "params: ${{ steps.branch-deploy.outputs.params }}"
     echo "parsed_params: ${{ steps.branch-deploy.outputs.parsed_params }}"
 ```
+
+## Parameters and Deployment Payloads
+
+All parameters (both parsed and raw) can be found in the `payload` of the actual deployment that gets created and stored on GitHub. You can read more about the deployment payload and its structure [here](./deployment-payload.md).