Adds definition for "short bus" per #433

[malchata]

Apologies for the long wait on the PR. It adds the definition for the ableist term "short bus" as proposed in issue #433. It also opportunistically removes an unnecessary crossorigin attribute on the rel=preload <link> elements in the header.

[tatianamac]

@malchata I know it's a hard habit to break but you don't owe me any apologies! I appreciate your contribution immensely!

I gave you a LOT of suggested changes—please feel free to accept/reject as makes sense to you. Most of it is preferential (in order to maintain a somewhat consistent approach between entries).

A few common patterns:

• I tried to balance people/students with I/DD and disabled people/students to address that there's no one-size term (and that generally my understanding is a larger portion of folks prefer to be called disabled over person-first language.)
• I restructured some passages in order to fit more consistently with the general theme we have for avoid-type words

Otherwise this was such a well thought-out entry! I think with one more pass (if you're able/willing) we'd be able to get this launched! ♥️

[tatianamac]

@malchata I think this mostly looks good to me! I'm curious if you intentionally omitted this suggestion or if it was missed? I don't feel strongly about it either way!

## Origins

While these school bus types are used to transport smaller groups of students to school or related activities, they may also be used to provide accessible transportation to students with intellectual and/or developmental disabilities (I/DD). The term became synonymous with mocking students with I/DD. It is also often used to imply ignorance, lack of understanding, or clumsiness (often in self-deprecation about the person using it).