issue templates

[juniperlsimonis]

sorry for the meta issue about issues, but i've created issue templates for the repo and would appreciate some editing assistance

the idea here is that we create templates for issues (and PRs, to come!) so that when specific features, bugs, questions, etc come up, there's an issue already started for someone to fill out and the relevant content, including assignees, is pre-filled

see the code and implementation

i could use specific assistance with identifying assignees for them. @gmyenni @henrykironde and @ethanwhite -- who should i pre-tag for these?

i'm happy to take any edits at all, but that's something i want to make sure we have squared away, so that when there's an issue, the right person gets notified