Muler

This release changes IGRINS input modes, adds more testing (including GitHub actions), and changes the dependencies based on insights from GitHub actions. Overall these changes should improve the stability and ease of installation of muler.

This release includes packaged template data for the first time. These templates are used for deblazing and sky subtraction based on calibration data. This package data should still work when installed with `pip`, though it should be considered experimental. As a fallback one may always follow the [developer instructions ](https://muler.readthedocs.io/en/latest/install.html).

We have completed a major refactor with the addition of a new EchelleSpectrum class, from which each instrument class inherits the majority of its behavior. The package has basic functionality that is useful for a wide range of quicklook and minimal pre-processing science applications.

The API should still be considered unstable. In particular we are likely to rename and retool the names of the classes for the SpectrumList-like objects. We eventually want to support lists of visits of spectra, rather than just lists of orders of a single spectrum. In making that change we are liable to rename lots of existing classes, which will break code.

We now have beta support for HPF! We are inviting beta testers to provide feedback. Thank you!