add utils::logical() function to complement the *numeric() functions

doc/src/Developer_utils.rst

@@ -60,6 +60,9 @@ silently returning the result of a partial conversion or zero in cases
 where the string is not a valid number.  This behavior allows to more
 easily detect typos or issues when processing input files.
 
+Similarly the :cpp:func:`logical() <LAMMPS_NS::utils::logical>` function
+will convert a string into a boolean and will only accept certain words.
+
 The *do_abort* flag should be set to ``true`` in case  this function
 is called only on a single MPI rank, as that will then trigger the
 a call to ``Error::one()`` for errors instead of ``Error::all()``
@@ -83,6 +86,9 @@ strings for compliance without conversion.
 .. doxygenfunction:: tnumeric
    :project: progguide
 
+.. doxygenfunction:: logical
+   :project: progguide
+
 
 String processing
 ^^^^^^^^^^^^^^^^^