Plot square or cube by default for geopandas Point/MultiPoint types

pygmt/src/plot.py

@@ -209,6 +209,8 @@ def plot(self, x=None, y=None, data=None, size=None, direction=None, **kwargs):
     extra_arrays = []
     if "S" in kwargs and kwargs["S"][0] in "vV" and direction is not None:
         extra_arrays.extend(direction)
+    elif "S" not in kwargs and kind == "geojson" and (data.geom_type == "Point").all():
+        kwargs["S"] = "s0.2c"
     if "G" in kwargs and not isinstance(kwargs["G"], str):
         if kind != "vectors":
             raise GMTInvalidInput(