[PROJ] proj manual, versioning, download location

[Greg Troxel]

The downloage page:

  https://proj.org/download.html

lists "PDF Manual" as being at:

  https://raw.githubusercontent.com/OSGeo/PROJ/gh-pages/proj.pdf

I wondered how it was versioned, and see that it is freshly generated
for 6.3.0.

It would be really nice if this were at

  https://download.osgeo.org/proj/

as

  proj-manual-6.3.0.pdf

or something like that.   This would make it easier to include in binary
packages, because:

  The file would be versioned, so that someone with e.g. 6.2.1 package
  control files could still build that package with the 6.2.1 manual.
  (In general, packaging systems aim to be reproducible, which leads to
  a ddislike of URLs with variable contents.)

  It would be downloadable from the same base URL, which makes life
  easier.

Thanks,
Greg