add libopenmpi-dev to installation instructions

[thekswenson]

I needed to install the Ubuntu libopenmpi-dev package in order to compile.

[bedroesb]

Thank you for this information. Could you specify which Ubuntu version you are using?

[thekswenson]

Ubuntu 24.10

[bedroesb]

Good to know you made it work for this recent Ubuntu version, let me see what I can do.