docs: make README punctuation more consistent (#5)

Author: ashtonav

README.md

@@ -32,8 +32,8 @@ This repository contains the source code for [AddressData.net](https://addressda
 
 ## Acknowledgments
 
-* **[Datasette](https://datasette.io/)**
-* **[Datasette Charcoal Theme](https://github.com/julien040/charcoal-datasette-theme)**
+* **[Datasette](https://datasette.io/)**.
+* **[Datasette Charcoal Theme](https://github.com/julien040/charcoal-datasette-theme)**.
 
 ## Contributing