Add html-pipeline-hashtag to 3rd party extensions [ci skip]
Add html-pipeline-hashtag to 3rd party extensions [ci skip]

Closes #226

kbrock/html-pipeline,kbrock/html-pipeline,gjtorikian/html-pipeline,github/html-pipeline,github/html-pipeline,jch/html-pipeline,jch/html-pipeline,gjtorikian/html-pipeline