Region map editor minor improvements

[meekrhino]

Using the region map editor for the first time in a long time and hit a couple of small things:

• I tried to use ctrl + scroll to zoom in and out, like we do in the main map editor. At first I thought there just was no zoom functionality when it didn't work. I know the slider to zoom is also common throughout porymap elsewhere, but in every case I think it would be beneficial to support ctrl + scroll zooming as well (e.g. metatile selector, tileset editor in both selection windows, etc)
• On the Map Entries tab, it would be great to be able to click on a tile in the map to select the MAP_SEC, rather than having to select it from the dropdown only. This is mainly helpful for modifying things once you already have a baseline so probably not the most common use case, but it would also be great for verifying that everything is as expected. I don't have a perfect answer to how to handle tiles with multiple MAP_SECs overlapping them, but I think even just arbitrarily picking one would be worthwhile. Ideal would probably be a way to show all the MAP_SECs that apply to a tile and letting the user pick from them, but I don't know what that would look like from a UI perspective.
• I'd love a button to edit the config for a Region next to the selection dropdown. It would open the Update Config modal with the current map selected. The Update Config... in the File menu isn't very intuitive to find, in my experience.
• This is more broad across all porymap, but I find it almost impossible to tell which tab I am on by looking at the tabs in dark theme specifically. The contrast is just a bit too low in my opinion. This is mainly on the "dark" theme; "default" is extremely clear, and "midnight" is slightly better than "dark" (but could still be improved).