Add Core Milestone Insights

[sommersoft]

Fixes #73

Was a simple fix, using the milestones API.

Core
* 10 pull requests merged
  * 5 authors - deshipu, penguindustin, dhalbert, sommersoft, siddacious
  * 2 reviewers - dhalbert, tannewt
* 8 open pull requests
  * https://github.com/adafruit/circuitpython/pull/1610
  * https://github.com/adafruit/circuitpython/pull/1600
  * https://github.com/adafruit/circuitpython/pull/1534
  * https://github.com/adafruit/circuitpython/pull/1423
  * https://github.com/adafruit/circuitpython/pull/1415
  * https://github.com/adafruit/circuitpython/pull/1365
  * https://github.com/adafruit/circuitpython/pull/1363
  * https://github.com/adafruit/circuitpython/pull/1274
* 6 closed issues by 2 people, 6 opened by 5 people
* 151 open issues
  * https://github.com/adafruit/circuitpython/issues
* 5 active milestones
  * 3.x: 1 open issues
  * 4.0.0 - Bluetooth: 16 open issues
  * 4.x: 19 open issues
  * Handheld Gaming: 6 open issues
  * Long term: 94 open issues
  * 15 issues not assigned a milestone

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[kattni]

Looks great! Thanks for adding this! 🌮