Add new guide on netCDF file format

[vmartinez-cu]

Created a guide about the netCDF file format pulling content written by Doug Lindholm. Confluence page

The content is mostly in the structure of bullet points. Some additional text is needed to provide context and explain how this file format is being used at LASP. I added a warning at the top of the guide noting that it's incomplete.

Details still needed:

• Expand overview section and explain bullet points
• Add a few sentences about the purpose of the guide
• Expand on options available
• Expand on how to apply the guide. Perhaps move the external links listed at the end of the guide to this section followed by tips and recommendations specific to LASP.
• Are there other useful links to add?

Credit is given to Doug at the bottom of the file, but we should figure out how best to do this since the structure is different from his original page

[vmartinez-cu]

I made some minor updates and added the guide to index.rst. I'll create a ticket for content still needed