Standardize on the Type field list items and allow filtering through and linking from them

[9ao9ai9ar]

The Type field that we fill in on the Event Editor shows up as grey text above the event cards in the timeline. They function like tags on a Stack Exchange site, and tags can be filtered and have descriptions added to on Stack Exchange. I guess this is a meta issue of 3 inter-related feature requests that I think would benefit the project:

1. A lot of work has already been done on MSE. For example, this post tries to list all the feature changes to Stack Exchange. Not all of them are important, of course, but everytime we introduce a feature-related event on the timeline, instead of linking to that MSE post from the individual events, we could have it written on the feature Type/tag itself, so interested readers know where to scavenge for the rest. To clarify, the Type is more like a Collective, and the Tags field can be included under a Type like Collective Tags. So for example, the Type feature (the name may not be finalized yet) can have the following related tags included under it: documentation and collectives (the tags should exist on a Stack Exchange website).

2. Standardize on the Type list item names. Currently, Stack Exchange launches "The Loop" has a loop type that is redundant (the the-loop tags should suffice), and I am sure there are many more (site-launch and site-graduation comes to mind). To prevent the Type list from proliferating further, we should carefully think through what "Types" we want to keep and turn them into selectable options instead of arbitrary text, and this leads me to the next proposal.

3. The Type should prove useful in that it could at least be used for filtering, like what we currently have at the top:

   show: [x] mod movements [x] staff movements [x] site graduations
   

   are the only filters, and their names don't even match the Types.

I know it is a big task to take on, but this was first on my mind after using the website for a couple of weeks, so it's like my user experience report.