Add virtual/hybrid/in-person tags for events

[klieret]

As suggested by @wdconinc

[klieret]

Looks good. Is there a use for a tag virtual, hybrid, in-person? Not sure how tags are defined and if we can just add them by text.

Unfortunately we'd need to switch a bit because of this:

 {% for tag in post.tags %} 
<a href="{{ '/training/our-events.html' | relative_url }}" title="Organized/supported by HSF">
<span class="badge badge-success">{{ tag }}</span></a>
 {% endfor %}

arguably a bad way of implementing the current system, too (mea culpa).

But basically the issue is that we'd need a merge of a second config of tag -> style, url and this might not be trivial.

One way could be to make this a separate extension and then have a long list of if, elif statements checking the type of tag that has been added... (or looping over a tag config and for every tag checking if it is included in the list of tags)
Another is to use one of the hacky ways to parse JSON in liquid (none of them seem much nicer than that)

Let me ping @henryiii if he can think of something quick & elegant