A very rough F21 alpha release announcement draft

[Joe Brockmeier]

Current draft here:

https://fedoraproject.org/wiki/F21_Alpha_release_announcement

A couple things that need to be filled out:

- More detail on each of the products.
- Anything we're missing that needs to be emphasized *during the alpha
release*?
- We don't currently have a F21 common bugs page.

I plan to give this one or more passes before I'd consider it final, but
I'd also like extra eyes, suggestions, etc.

Best,

jzb