Add skycoord param

[bhazelton]

Description

Use a skycoord parameter for sky location information.

Motivation and Context

closes #119 closes #127

Checklists:

New Feature Checklist:

• [x] I have read the contribution guide.
• [x] My code follows the code style of this project.
• [x] I have added or updated the docstrings associated with my feature using the numpy docstring format.
• [x] I have updated the tutorial to highlight my new feature (if appropriate).
• [x] I have added tests to cover my new feature.
• [x] My change includes a breaking change
  • [x] My change includes backwards compatibility and deprecation warnings (if possible).
• [x] I have updated the CHANGELOG.

[codecov[bot]]

Codecov Report

Base: 99.67% // Head: 99.87% // Increases project coverage by +0.19% :tada:

Coverage data is based on head (0d7502f) compared to base (cb2ee30). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #186 +/- ## ========================================== + Coverage 99.67% 99.87% +0.19% ========================================== Files 6 6 Lines 2176 2401 +225 ========================================== + Hits 2169 2398 +229 + Misses 7 3 -4 ``` | [Impacted Files](https://codecov.io/gh/RadioAstronomySoftwareGroup/pyradiosky/pull/186?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=RadioAstronomySoftwareGroup) | Coverage Δ | | |---|---|---| | [pyradiosky/skymodel.py](https://codecov.io/gh/RadioAstronomySoftwareGroup/pyradiosky/pull/186?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=RadioAstronomySoftwareGroup#diff-cHlyYWRpb3NreS9za3ltb2RlbC5weQ==) | `100.00% <ø> (+0.20%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=RadioAstronomySoftwareGroup). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=RadioAstronomySoftwareGroup)

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[bhazelton]

Ok @mkolopanis I think I addressed all your comments.