Add a stand-alone example build with osal (modernize src/examples/ tasking-example?)

[skliper]

Is your feature request related to a problem? Please describe.
Difficult for new user to set up a new trivial build using just OSAL.

Describe the solution you'd like
Helpful to include a simple CMake setup and a bare-bones c file to show simplest version of OSAL use. There's src/examples, but it's not set up to build/run out of the box. Also update the instructions in the users guide.

Describe alternatives you've considered
None.

Additional context
None.

Requester Info
Jacob Hageman - NASA/GSFC - Stakeholder request

[astrogeco]

@skliper Does #812 fix this?

[skliper]

@skliper Does #812 fix this?

No. #812 does supply the sample cmake instructions, but this is to actually add something that will build/run. Even better if the example build is added to CI so it doesn't rot.