Add configuration file reference

docs/references/configuration-file.md

@@ -1 +1,41 @@
 # Configuration file
+
+## `pageship.toml`
+
+`pageship.toml` is the main configuration file used by Pageship. All paths
+referenced in `pageship.toml` is resolved relative to its location.
+
+### `app` section
+
+The `app` section defines the app config when hosted in managed-sites mode
+server.
+
+- `app.id`: Unique ID of the app in the server.
+- `app.team`: ACL rules controlling API access of app management.
+    - `app.team[].access`: Access level of the actor matching the rule (highest level applies):
+        - `reader`: read-only access to app metadata (e.g. list of deployments/sites)
+        - `deployer`: access neccessary for deploying sites
+        - `admin`: full access to the app
+- `app.defaultSite`: The name of main site (default to `main`).
+- `app.sites`: The available sites in the app, the main site can be accessed
+  through the app domain, while other sites is accessed through a subdomain.
+      - `app.sites[].name`: the site name, cannot be used with pattern.
+      - `app.sites[].pattern`: the site name pattern, cannot be used with name.
+  subdomain.
+- `app.deployments`: Configuration for preview deployments
+    - `access`: ACL rules controlling access of preview deployments.
+    - `ttl`: the lifetime of a preview deployment (default to `24h`)``
+
+### `site` section
+
+The `site` section defines the site config.
+- `site.public`: The path to site directory
+- `site.access`: ACL rules controlling access of site
+
+
+## `sites.toml`
+
+`sites.toml` is used for unmanaged-sites mode. It defines the location and
+resolution of multiple apps.
+- `sites.<name>`: The list of sites to serve
+    - `sites.<name>.context`: directory of the site.