acknowledge allejo

README.md

@@ -16,6 +16,10 @@ under the [Center for Scientific Collaboration and Community Engagement's][cscce
 concept of a *Community Playbook*, as part of the
 [CSCCE Community Engagement Fellows Program][cefp-homepage] 2019 (CEFP2019).
 
+We use `toc.html` taken from
+[this amazing repo from GitHub user _allejo_](https://github.com/allejo/jekyll-toc)
+under an MIT license to generate in-page table of contents.
+
 ## Build info
 
 The [site][docs] is built with [Jekyll][jekyll]