Adds basic blog functionality

[jorydotcom]

Closes #309

Adds:

• _posts directory + collection
• 'Blog' to main nav
• Layouts for post pages, post-list

Note:
I am not a designer 😂 but see attached screenshots; need to nuke _posts before merging (unless someone wants to merge with an inaugural blog post!)

Signed-off-by: Jory Burson jburson@linuxfoundation.org

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[TomHennen]

Thanks so much! @MarkLodato did you want to review this or are you happy for someone else to do so?

[inferno-chromium]

Thanks so much! @MarkLodato did you want to review this or are you happy for someone else to do so?

@TomHennen feel free to review as well. Also, i think some minor layout things can be improved (e.g. spacing before each blog title, split row colors e.g. on overview page, etc), this can be come in next CL.

[MarkLodato]

Thanks, Jory! I think this is great.

Note that the spacing between paragraph is bad due to #335, if anyone is willing to fix that in a separate PR.