Add inline example for grdproject (#1722)

Author: willschlitzer

pygmt/src/grdproject.py

@@ -95,6 +95,21 @@ def grdproject(grid, **kwargs):
         - :class:`xarray.DataArray` if ``outgrid`` is not set
         - None if ``outgrid`` is set (grid output will be stored in file set by
           ``outgrid``)
+
+    Example
+    -------
+    >>> import pygmt  # doctest: +SKIP
+    >>> # Load a grid of @earth_relief_30m data, with an x-range of 10 to 30,
+    >>> # and a y-range of 15 to 25
+    >>> grid = pygmt.datasets.load_earth_relief(
+    ...     resolution="30m", region=[10, 30, 15, 25]
+    ... )  # doctest: +SKIP
+    >>> # Create a new grid from the input grid, set the projection to
+    >>> # Mercator, and set inverse to "True" to change from "geographic"
+    >>> # to "rectangular"
+    >>> new_grid = pygmt.grdproject(
+    ...     grid=grid, projection="M10c", inverse=True
+    ... )  # doctest: +SKIP
     """
     if "J" not in kwargs:
         raise GMTInvalidInput("The projection must be specified.")