Fix the /paths from absolute to relative in HTMLFix paths

Fixes StackStorm/stackstorm.com#5

A few caveats/heads-up/feedback:

The #community URL fragment is linked with a target="_blank" attribute, which could still make sense for other pages, but on the home page that the fragment belongs to, it looks weird.
There is an odd link that look likes an email but is put under the current directory's path (/2021/12/16/stackstorm-v3-6-0-released/Aaron.jonen@cypherint.com). I left it as it is. Not sure if there are more like that.
There are broken links found across the repo (such as /start-now/ and /news-events/) mostly directly below the root level. I have fixed the relative path for them anyway. I haven't found/made a note of all such broken links.
There are also a couple other broken links caused by what seem to be obsolete/time-sensitive pages that are no longer there (example: /meeting-registration-tuesday-july-22-1130-pdt at /2014/07/23/stackstorm-devops-automation-interactive-webinars-register-today/index.html. I have fixed their relative paths as well, FWIW.
There is a broken reference to a non-existent wp-json directory/file in so many <link> tags across the codebase, but never within an <a> tag. I left it as it is.

StackStorm / stackstorm.com