UG cleanup of alert calls: drop color when set to default

[chalin]

• Cleanup in prep for A better alert shortcode more markdown friendly #941
• Drops color="primary" since that's the default for the alert shortcode.
• Added _build NPM script

No changes to generated site files (this was run before fix:format changes were committed):

$ (cd public && git diff -bw --ignore-blank-lines -I "dateModified|modified_time|data-proofer" -- ':(exclude)*.xml')
$ (cd public && git diff) | grep ^diff | wc -l                                             
       8