Make ping and issues triggers check for more specific messages

[sethetter]

Right now the ping and issues triggers will fire if the bot is mentioned in the message, and anywhere in the message text contains the strings ping or issues, which can result in a lot of false positives.

Update the filters for those triggers to check that the message equals exactly <@BOT-ID> ping (or issues) instead of using just CONTAINS.

Here are the Slack docs on trigger filters.

[melicent]

I'm interested in working on this (please let me, I'm a typescript noob)

[sethetter]

@melicent it's yours! :)

[JayGaba]

@sethetter I would like to work!

[JayGaba]

@sethetter could you review the changes please!