Add fetch_depth value to the GitHub checkout action

As mentioned in the mkdocs-git-revision-date-localized-plugin
(https://goto.corp.avm99963.com/9w8kv6), if using Github as a CI the
plugin will not be able to retrieve the last modified date if the
fetch_dept option is not set to 0.

Change-Id: I5f4dd0ba90160884aae71177b37f3bbfcd7602de
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index b37f858..7b26faa 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -11,6 +11,8 @@
     steps:
       - name: Checkout master
         uses: actions/checkout@v2.3.4
+        with:
+          fetch-depth: 0
 
       - name: Deploy docs
         uses: mhausenblas/mkdocs-deploy-gh-pages@1.16