Add OpenACC link options to io shared library

[DuttaS12]

The io library contains OpenACC pragmas (e.g., in write_mo_grid) but was missing -acc=gpu in target_link_options. For shared libraries with OpenACC code, the link options are required in addition to compile options.

• Implement changes
• Update documentation
• Update tests
• Look through pull request changes
• Clean up code and retest
• Increment version number

Closes ISSUE
This pull request makes a small update to the build configuration for GPU acceleration in the src/libio/CMakeLists.txt file. The change ensures that when GPU acceleration is enabled, the linker is also passed the appropriate -acc=gpu flag.

• Build configuration: Added target_link_options(io PRIVATE -acc=gpu) to ensure the linker receives the GPU acceleration flag when USE_ACC is enabled.

Note: The write_mo_grid() function is the first function within that folder that used OpenACC which is why this change was needed