ENH: Improve calc_measured_loc performance and support

[aburrell]

Description

Expands the applicability of the pysatMadrigal.instruments.methods.jro.calc_measured_loc routine to more az/el variable names, adds an example to the docs, and adds unit tests for pysatMadrigal.instruments.methods.jro.

Partially addresses #3 and #41.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality or documentation)
• This change requires a documentation update

How Has This Been Tested?

Created an example, which you can follow along in ex_jro_isr_beam.rst to reproduce a figure. Also added unit test to test_methods_jro.py.

Test Configuration

• Operating system: OS X Mojave
• Version number: Python 3.9
• Any details about your local setup that are relevant

Checklist:

• Make sure you are merging into the develop (not main) branch
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have linted the files updated in this pull request
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Add a note to CHANGELOG.md, summarizing the changes

If this is a release PR, replace the first item of the above checklist with the
release checklist on the pysat wiki:
https://github.com/pysat/pysat/wiki/Checklist-for-Release

[jklenzing]

This looks good. Some suggestions below for consistency across projects.