[Halld-npp] NPP proposal on GitHub

[Mark Ito]

Folks,

I grabbed a snapshot of the NPP proposal from the Overleaf site just now 
and put it on GitHub. You can find it here:

https://github.com/markito3/pi0_polarizability_proposal

It is on the master branch and I have also created a tag/release:

https://github.com/markito3/pi0_polarizability_proposal/releases/tag/v2

The release notes reference version 2 on the DocDB. Note that the GitHub 
repository only contains the raw LaTex files and the figures. There is 
no PDF here, but there is a makefile you can use to create one.

   -- Mark