Add docstring for position parameter

Author: yvonnefroehlich

pygmt/src/pygmtlogo.py

@@ -296,7 +296,18 @@ def pygmtlogo(  # noqa: PLR0913
         Set the width of the logo.
     hight
         Set the hight of the logo.
-    $position
+    position
+        Position of the GMT logo on the plot. It can be specified in multiple ways:
+
+        - A :class:`pygmt.params.Position` object to fully control the reference point,
+          anchor point, and offset.
+        - A sequence of two values representing the x- and y-coordinates in plot
+          coordinates, e.g., ``(1, 2)`` or ``("1c", "2c")``.
+        - A :doc:`2-character justification code </techref/justification_codes>` for a
+          position inside the plot, e.g., ``"TL"`` for Top Left corner inside the plot.
+
+        If not specified, defaults to the Bottom Left corner of the plot (position
+        ``(0, 0)`` with anchor ``"BL"``).
     box
         Add a box around the logo.
     $verbose