A new documentation for the CTSM dust emission module

[dmleung]

… New CTSM dust emission documentation by @dmleung.

Description of changes

This PR is on updating the ctsm tech note / documentation on the CTSM dust emission modules, Leung_2023 and Zender_2003.

Specific notes

Contributors other than yourself, if any: @samsrabin @ekluzek @tilmes

CTSM Issues Fixed (include github issue #): #3170

Are answers expected to change (and if so in what way)? No, this is a documentation to the dust emission module

Any User Interface Changes (namelist or namelist defaults changes)? No

Does this create a need to change or add documentation? Did you do so? This PR is on changing the documentation.

Testing performed, if any:

[dmleung]

Hi @samsrabin I do need to make a few more commits to clean up the doc, check section numbers, and add references before it's ready for review. I will make updates soon, but I do want to put a draft PR here. Thanks!

[ekluzek]

I rebased this to come to b4b-dev rather than master.

[ekluzek]

I rebased this to come in on b4b-dev rather than master.

[dmleung]

Oh, I don't know we are merging to b4b-dev. Thanks for doing that Erik!