Dev telecons for triaging/prioritization of core astropy #94

Suggested by: @eteq
Expanded by: @pllim (feel free to edit if I got things wrong)

Motivations:

1. When contributors want to contribute, they know which issues are important and hopefully will work on those instead of picking a random thing they find on issues; e.g., I think LSST has asked for this in the past, as well as other interested parties.
2. Assist core maintainers on which issue/PR needs to be worked on for the next release and which one can slip if need be.

Execution:

1. Set up telecons at a cadence, where maintainers can attend to prioritize issues for the subpackages they are responsible for.
2. Require a critical mass of core maintainers for effective triaging.

Risks:

1. Critical mass not achieved due to poor turnout. (Like the dev telecons.)
2. The people who show up prioritize things in a way that does not align with the project as a whole (e.g., biased by goals set by their own employers/institutions).
3. No momentum to continue prioritization as new issues come in for the foreseeable future, resulting in partial prioritization, where some important issues are not being recognized as such.
4. People ignore the labels anyway.