TST: add workflow_dispatch for pysat RC

[jklenzing]

Description

Addresses pysat/pysat#1042

Adds a dispatch workflow to test this package with the latest pysat RC.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Inspecting the logs at https://github.com/pysat/pysatMissions/actions/runs/3439753149

Ensure that pysat is installed only from the test pypi server.

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 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