[APT-1781] Add TFC/TFE integration guide (#250)

* [APT-1781] Add TFC/TFE integration guide

* Add guide on using/wrapping Gruntwork modules, and clean up cross links with TFC/TFE guide.

* Update _docs-sources/intro/dev-portal/link-github-id.md

* Rephrase GitHub linking page and update hash correctly

Author: ebeneliason

_docs-sources/guides/build-it-yourself/index.md

@@ -44,9 +44,13 @@ The Gruntwork IaC library empowers you to construct your own bespoke architectur
 ## Dig Into the Code
 
 <Grid cols={2}>
-  <Card title="Browse Services" href="/reference/services/intro">
+  <Card title="Browse Gruntwork Services" href="/reference/services/intro/overview">
     View the API reference for our entire service catalog to learn what’s
-    available.
+    available out-of-the-box.
+  </Card>
+  <Card title="Create Your Own Services" href="/guides/working-with-code/using-modules">
+    Learn how to wrap one or more Gruntwork modules to create modules and
+    services that fit your needs.
   </Card>
   <Card
     title="View the Code in GitHub"