create alias swim_shirt -> rash_guard
I was a little split on whether to go from swim shirt --> rash guard or the other way around, but I ultimately chose rash_guard and made a wiki page for it. I did this for several reasons.
1. Rash guard is the proper name of the garment.
2. Pixiv uses the rash_guard tag ラッシュガード
3. Wikipedia also uses rash_guard over swim_shirt: https://en.wikipedia.org/wiki/Rash_guard
4. If you go to amazon and enter "swim shirt" you will automatically be given results that all say "rash guard or rashguard".
So, a rash guard is sometimes called a swim shirt. Not the other way around.
That's my argument anyway. Either way, the two need to be aliased/merged. The combined numbers will help justify a tag in the first place.
I could just go and re-tag the images, but I think keeping swim_shirt as an alias will help direct people to the actual name of the garment. I know I've needed help a few times! The alias system works very well.
Updated by user 266329