Update CI_build.yml

Change name to "Build Static HTML for Verification".
Only run for pull requests and workflow_dispatch, to avoid doing so much hugo/httrack downloading -- that way, it's only when reviewers want to view the HTML from a contributor, or someone wants to manually check the results of their change without using a local hugo.exe; don't need to waste CPU cycles when the HTML was already verified from a local hugo server during development.

.github/workflows/CI_build.yml

@@ -1,6 +1,6 @@
-name: CI_build
+name: Build Static HTML For Verification
 
-on: [push, pull_request]
+on: [pull_request, workflow_dispatch]
 
 jobs:
   build: