Update web page after Astropy APE

[willingc]

From #258 (comment)

i've also created a local task to do a bit more web dev when we add the astropy landing page to our site (after the APE is approved)

it will look something like this:

BACKEND dev

• add a small module to update-web-meta with a last_activity_date.
• this would parse a github repo and determine the latest date of a pr, commit or release
• the above would add a field to the packages.yml file last_activity_date

FRONT END DEV (what people see on the website)

• parse the yaml file
• find that field, and
• for each package, if the date is older than 12 months, add a orange flag to the package card then simply add a key / explanation to the website that tells the user what the flag means.

[lwasser]

thank you @willingc for adding this issue!