Add the document for serialization

Author: noah

docs/concepts/deploy.yml.md

@@ -66,6 +66,15 @@ envs:
         location: Asia/Seoul
 ```
 
+### Serialization
+**Serialization forces only one deployment to run for the same environment.** If deployment is running for a specific environment, users cannot deploy until the deployment is finished. In particular, serialization is helpful in long-running deployment strategies, such as canary deployments, as it prevents other deployments.
+
+```yaml title="deploy.yml"
+envs:
+  - name: production
+    serialization: true
+```
+
 ### Review
 If you require a specific person, such as a service owner or product manager, to review what is deployed before deployment, you can configure the `review` field. You can list up users as reviewers under the `review` field. Then Gitploy requests a review to users by sending a notification when a deployment is triggered.
 

docs/references/deploy.yml.md

@@ -23,7 +23,7 @@ Field                    |Type                     |Required  |Description
 `production_environment` |*boolean*                |`false`   |This field specifies whether this runtime environment is production or not.
 `deployable_ref`         |*string*                 |`false`   |This field specifies which the ref(branch, SHA, tag) is deployable or not. It supports the regular expression `re2`. 
 `auto_deploy_on`         |*string*                 |`false`   |This field controls auto-deployment behaviour given a ref(branch, SHA, tag). If any new push events are detected on this event, the deployment will be triggered. It supports the regular expression ([re2](https://github.com/google/re2/wiki/Syntax)). E.g. `refs/heads/main` or `refs/tags/v.*`
-`review`                 |*[Review](#review)*      |`false`   |This field configures reviewers.
+`deployable_ref`         |*string*                 |`false`   |This field specifies which the ref(branch, SHA, tag) is deployable or not. It supports the regular expression `re2`. 
 `frozen_windows`         |*[\][Frozen Window](#frozen-window)* |`false`   |This field configures to add a frozen window to prevent unintended deployment for the environment.
 
 ## Review