Refactor: hidden logic in runes.js code

[cannawen]

• [x] The string we return relies (non-obviously) on the order of the if statements
• [x] There is hidden logic to not announce the 0 minute bounty is within this code.
• [x] Investigate having a { start-time, end-time, interval } object for each rune to uniquely identify if it will spawn or not.
• [X] Could potentially programatically construct the announcement string if bounty and power runes spawn at the same time wontfix
• [X] runes.js could be returning a data structure for someone else to turn into human-readable strings
• [x] GSI event strings should be sequestered
• [X] have a file with pure runes logic and two files with glue to/from Discord/GSI. Maybe 3 files in one folder?
• [x] how do we want to deal with these magic numbers ESLint keeps complaining about?

Related story #1

[cannawen]

I think the code has been sufficiently factored to close this story. Game rune logic is completely separated from discord/gsi logic, with beautiful tests

And answer to how to deal with eslint not liking magic numbers? Disabling the eslint rule for the block xd