Add theme as git submodule

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "site/themes/hugo-theme-learn"]
+	path = site/themes/hugo-theme-learn
+	url = https://github.com/matcornic/hugo-theme-learn.git

README.md

@@ -6,7 +6,11 @@ This workshop teaches you best practices for using ECS Fargate.  It has three in
 * Operations
 * Data engineering
 
-The full documentation is available in the `site` folder, and is best viewed with [Hugo](https://learn.netlify.app/en/basics/).  You can run Hugo locally by downloading Hugo for your platform, going to the `site` folder, and running `hugo serve`.
+The full documentation is available in the `site` folder, and is best viewed with [Hugo](https://learn.netlify.app/en/basics/).  You can run Hugo locally by following these steps:
+
+1. Download all dependencies by running `git submodule init` and `git submodule update`. If you run this a second time, you only have to do the latter.
+2. Downloading Hugo for your platform.
+3. Go to the `site` folder, and run `hugo serve`.
 
 ## License Summary