Add Mount Laguna Observatory to sites registry

[cgobat]

Description

This pull request adds Mount Laguna Observatory (website; Wikipedia) to the sites.json registry.

[hamogu]

On https://www.google.com/maps/@32.8424,-116.428,391m/data=!3m1!1e3!5m1!1e2
it looks as if this is the northernmost dome (unnamed on Google maps) while Mount Laguna is about 600 ft more to the south. Not a huge difference, and I don't know the observatory, so I just want to check if these coordinates make more sense, e.g. because they are consistently used by all observers?
Or should we maybe use the location that google calls "SDSU observatory" which is kind of in the middle between the two other telescopes?
You are in San Diego, so you probably have some insider knowledge, and I will merge whatever you think is best, but I just wanted to bring it up to be sure.

[cgobat]

Yeah, fair point. All of the domes there are technically part of the observatory as a whole, but I just updated the last digits to land closer to the main/largest dome. I don't think it makes sense to go much beyond 4 decimal places on the lat/lon.

Thanks for the suggestion—I had erred on the side of going with exactly what Wikipedia listed, but this is better since almost all of the science data currently collected at the observatory is taken by that main telescope, and it's closer to the central point of the footprint of the overall observatory either way.

[hamogu]

Thanks a lot @cgobat !