message: add link to uberenv docs
diff: @@ -57,6 +57,8 @@ Some helpful uberenv options include :
  * ``--spack-config-dir=<Path to spack configuration directory>`` (use specific Spack configuration files)
  * ``--prefix=<Path>`` (required, build and install the dependencies in a particular location)
  +There is more thorough `uberenv documentation here <https://uberenv.readthedocs.io/en/latest/>`_.
  +
  The modifiers to the Spack specification ``spec`` can be chained together, e.g. ``--spec=%clang@10.0.0+debug+devtools``.
  If you already have a Spack instance from another project that you would like to reuse,
  