Added a collection for all transgender creations

I already had some collections of other people's zines, games, and other creations about specific transgender identities: trans women, trans men, and nonbinary. Sorting these into separate categories is useful for finding something specific that you want to read or play. Not all creations about trans people can or should be divided into these categories. Also, as trans people, it is not in our best interests to be divided. Solidarity and diversity are important. With those thoughts, I just made a new collection for all transgender creations.