chore(deps): bump skyfield from 1.36 to 1.37

[dependabot]

Bumps skyfield from 1.36 to 1.37.

Changelog

Sourced from skyfield's changelog.

v1.37 — 2021 February 15

• Added a :meth:~skyfield.positionlib.ICRF.frame_latlon_and_rates() method that can compute the rates at which angles like altitude and azimuth, or right ascension and declination, are changing.

• Accepted a contributor’s helpful fix for a rounding error that had slightly shifted a few constellation boundaries. [#548](https://github.com/brandon-rhodes/python-skyfield/issues/548) <https://github.com/skyfielders/python-skyfield/issues/548>_

• The :class:~skyfield.timelib.Time tuple :data:~skyfield.timelib.Time.utc and method :data:~skyfield.timelib.Time.utc_strftime() are now backed by the same math, so they always advance to the next calendar day at the same moment. This makes it safe to mix values returned by one of them with values returned by the other. [#542](https://github.com/brandon-rhodes/python-skyfield/issues/542) <https://github.com/skyfielders/python-skyfield/issues/542>_

• Vector subtraction now returns the position subclass specific to the resulting vector’s center. [#549](https://github.com/brandon-rhodes/python-skyfield/issues/549) <https://github.com/skyfielders/python-skyfield/issues/549>_

Commits

• 38bd9e0 Declare 1.37
• 9fbcba4 Update changelog for release
• 4b8fd8a Set specific result classes for vector subtraction
• 2c05c63 Switch almanac routines to new “step_days” param
• 71f0734 Add Solar Noon example to documentation
• 78d2afc Respell “Longnitude” as “Longitude”
• 97dd764 Add alt/az rates: perfect match with HORIZONS!
• 6e79462 Fix badly rounded constellation boundaries (#548)
• dd4ec5b Add new frame_latlon_and_rates() to main API docs
• b62ad3f Document new AngleRate and Rate classes
• Additional commits viewable in compare view

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[coveralls]

Coverage remained the same at 90.363% when pulling 5c2f1e3 on dependabot/pip/master/skyfield-1.37 into 4b92fb5 on master.