message: tweaks to change #->$ and other details in README-DOCKER
diff: @@ -27,7 +27,7 @@ $ docker run -it ghcr.io/mfem/mfem-ubuntu bash
  Off the bat, you can see mfem libraries are in your path so you can jump into development:
  ```bash
  -env | grep MFEM
  +env | grep mfem
  ```
  ```bash
  PKG_CONFIG_PATH=/opt/mfem-env/.spack-env/view/lib/pkgconfig:/opt/mfem-env/.spack-env/view/share/pkgconfig:/opt/mfem-env/.spack-env/view/lib64/pkgconfig
  @@ -57,7 +57,7 @@ You can find the examples here:
  cd share/mfem/examples
  ```
  ```bash
  -# ./ex0
  +$ ./ex0
  Options used:
  --mesh ../data/star.mesh
  --order 1
  @@ -82,7 +82,7 @@ You can also explore the "mini apps," also in share/mfem, but under miniapps.
  $ cd ../miniapps
  ```
  ```bash
  -# ls
  +$ ls
  CMakeLists.txt common meshing nurbs shifted toys
  adjoint electromagnetics mtop parelag solvers
  autodiff gslib navier performance tools
  @@ -94,7 +94,7 @@ And an example in "toys"
  cd toys
  ```
  ```bash
  -# ./automata
  +$ ./automata
  Options used:
  --num-steps 16
  --rule 90
  