[readme] update HTTPS instructions

Fixes #37

Author: ljharb

README.md

@@ -17,7 +17,7 @@ Follow these steps:
   1. Go to your repo settings page:
       1. Under “General”, under “Features”, ensure “Issues” is checked, and disable “Wiki”, and “Projects” (unless you intend to use Projects)
       1. Under “Pull Requests”, check “Always suggest updating pull request branches” and “automatically delete head branches”
-      1. Under the “Pages” section on the left sidebar, and set the source to “deploy from a branch” and check “Enforce HTTPS”
+      1. Under the “Pages” section on the left sidebar, and set the source to “deploy from a branch”, select “gh-pages” in the branch dropdown, and then ensure that “Enforce HTTPS” is checked.
       1. Under the “Actions” section on the left sidebar, under “General”, select “Read and write permissions” under “Workflow permissions” and click “Save”
   1. [“How to write a good explainer”][explainer] explains how to make a good first impression.