make `main` default

[sneakers-the-rat]

I guess there wasn't a main branch or something? in any case I made a branch init-myst and it became the default branch. can we change the default branch back to main?

I also intended to PR init-myst instead of pushing to main, but, well, here we are!

[sneakers-the-rat]

@rly any way ya could make me admin on this repo? i'm gonna get started

[rly]

That's not possible for personal repositories. How about I transfer the repo to you? Or we create an organization and both be admins there?

[sneakers-the-rat]

either way :) if it's not too much trouble let's do the org route just so we can all be admins

[rly]

I moved the repo to the linkml org and Chris made us both admins. We can make main default again. I'm not sure why it wasn't the default before...