Add lastReleaseDate response in GraphiQL > metricActivity() method

[hncslwx]

People want to know if an OS project is keeping its pace on release new version, last release date of this OS project can be used to judge this activity.
When this date to current date is longer than its normal period, risk is going up until it release a new version.

[eyehwan]

A nice suggestion! @coder-sett we also need to add it on the overview dashboard.