Add a first pass at a modal refill

[creuter]

• Closes when pressing escape, clicking the close button, or clicking the overlay
• focuses into the modal when opening
• focuses back to the open button when closing

[drapergeek]

Code LGTM

[creuter]

@tysongach Yeah, I'm not sure either. Even when explicitly focusing onto the title, it's not reading it, and I'm not sure what I'm missing.

Mindpatterns follows the same pattern I did here: http://ianmcburnie.github.io/mindpatterns/disclosure/dialog/index.html

[ghost]

I found 1 accessibility errors:

'http://localhost:4567/ | critical | Form elements must have labels | ["#dropdown-snippets > div:nth-of-type(1) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#dropdown-snippets > div:nth-of-type(2) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#dropdown-snippets > div:nth-of-type(3) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#modal-snippets > div:nth-of-type(1) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#modal-snippets > div:nth-of-type(2) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#modal-snippets > div:nth-of-type(3) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#tooltipped-snippets > div:nth-of-type(1) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input", "#tooltipped-snippets > div:nth-of-type(2) > .snippet-code.ace_editor.ace-tomorrow > .ace_text-input"]'