Added alias for F in basemap (#1894)

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>
Co-authored-by: Wei Ji <23487320+weiji14@users.noreply.github.com>

pygmt/src/basemap.py

@@ -21,6 +21,7 @@
     JZ="zsize",
     B="frame",
     L="map_scale",
+    F="box",
     Td="rose",
     Tm="compass",
     U="timestamp",
@@ -61,6 +62,24 @@ def basemap(self, **kwargs):
         [**g**\|\ **j**\|\ **J**\|\ **n**\|\ **x**]\ *refpoint*\
         **+w**\ *length*.
         Draws a simple map scale centered on the reference point specified.
+    box : bool or str
+        [**+c**\ *clearances*][**+g**\ *fill*][**+i**\ [[*gap*/]\ *pen*]]\
+        [**+p**\ [*pen*]][**+r**\ [*radius*]][**+s**\ [[*dx*/*dy*/][*shade*]]].
+        If set to ``True``, draws a rectangular border around the
+        map scale or rose. Alternatively, specify a different pen with
+        **+p**\ *pen*. Add **+g**\ *fill* to fill the scale panel [default is
+        no fill]. Append **+c**\ *clearance* where *clearance* is either gap,
+        xgap/ygap, or lgap/rgap/bgap/tgap where these items are uniform,
+        separate in x- and y-direction, or individual side spacings between
+        scale and border. Append **+i** to draw a secondary, inner border as
+        well. We use a uniform gap between borders of 2p and the
+        :gmt-term:`MAP_DEFAULTS_PEN` unless other values are specified. Append
+        **+r** to draw rounded rectangular borders instead, with a 6p corner
+        radius. You can override this radius by appending another value.
+        Finally, append **+s** to draw an offset background shaded region.
+        Here, *dx/dy* indicates the shift relative to the foreground frame
+        [Default is 4p/-4p] and shade sets the fill style to use for shading
+        [default is gray50].
     rose : str
         Draws a map directional rose on the map at the location defined by
         the reference and anchor points.