DOC: Add design idea of PyGMT logo to docstrings (#4719)

Co-authored-by: Michael Grund <23025878+michaelgrund@users.noreply.github.com>

Author: yvonnefroehlich

pygmt/src/logo.py

@@ -97,6 +97,11 @@ def logo(  # noqa: PLR0913
     $perspective
     $transparency
 
+    See Also
+    --------
+    pygmt.Figure.pygmtlogo
+        Plot the PyGMT logo.
+
     Examples
     --------
     >>> import pygmt

pygmt/src/pygmtlogo.py

@@ -291,8 +291,17 @@ def pygmtlogo(  # noqa: PLR0913
     """
     Plot the PyGMT logo.
 
+    .. figure:: https://raw.githubusercontent.com/GenericMappingTools/pygmt/main/doc/_static/pygmtlogo.png
+       :alt: PyGMT logo
+       :align: center
+       :width: 400px
+
     The design of the logo is kindly provided by `@sfrooti <https://github.com/sfrooti>`_
-    and consists of a visual and the wordmark "PyGMT".
+    and consists of a visual and the wordmark "PyGMT". The outer shape (in Python blue)
+    represents Earth, with compass lines (in Python yellow) surrounding the letters
+    "GMT" (in the red used for the GMT logo). The letter "T" aligns with the needle of
+    the compass. By default, the PyGMT logo is plotted without wordmark, with a size of
+    2 centimeters for the circular version of the icon.
 
     Parameters
     ----------
@@ -338,6 +347,11 @@ def pygmtlogo(  # noqa: PLR0913
     $perspective
     $transparency
 
+    See Also
+    --------
+    pygmt.Figure.logo
+        Plot the GMT logo.
+
     Examples
     --------
     >>> import pygmt