Add filtering by location to the conference page

[vasnt]

• Just like location, date can be added in a separate column.

• Also filtering can be added for location & date.

[anze3db]

Just like location, date can be added in a separate column.

I had it that way at first, but then changed it to a joint name/date column to save space on mobile, that's more than 60% of traffic and the space is very limited:

Also filtering can be added for location & date.

The locations are a bit of a mess right now so I'll have to standardize it before filtering will be possible and I was planning to add filtering by year once I have conferences for multiple years (probably beginning of 2025).

I want to add both of the filters at some point, but it's not a high priority right now since there isn't all that many conferences yet!