Add directory for info architecture proposals and first two proposals

[dempseyatgithub]

As discussed in the last website workgroup meeting, Swift info architecture project proposals and documents will be included in the swift-org-website repository.

The proposals are not rendered as webpages on swift.org.

Jekyll automatically ignores directories and files beginning with #. Since files beginning with an underscore are typically part of the configuration / operation of Jekyll itself, the directory name is #info-architecture to emphasize this is not part of the Jekyll infrastructure or published on the website.

This PR includes the first two proposals that have been announced and reviewed by the community. Future proposals will be added when they are ready for community review and feedback.

[heckj]

Content is great, but would you mind terribly if we switched the prefix from # to _, as the # symbol is causing no end of pain for me when I'm trying to interact with it on the command line.

Plus, that keeps in line with the other "ignored" directories that need to be explicitly included per config (https://jekyllrb.com/docs/structure/)

[dempseyatgithub]

@heckj I changed the prefix to _. Items prefixed by # are also automatically excluded by Jekyll, but if that makes it much more difficult to use on the command line, let's change it. Was trying to differentiate it from a directory that was part of Jekyll's infrastructure or a directory that has content intended for the site.

I'm fine with using _.