ppmdraw, ppmglobe, pnmmercator: add pages (#15357)

* fix ci

* ppmdraw, ppmglobe, pnmmercator: add pages

* Apply suggestions from code review

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/ppmglobe.md

@@ -0,0 +1,13 @@
+# ppmglobe
+
+> Generate strips of an image suitable to be glued onto a sphere.
+> See also: `pnmmercator`.
+> More information: <https://netpbm.sourceforge.net/doc/ppmglobe.html>.
+
+- Transform an image to strips that can be cut out and glues onto a sphere:
+
+`ppmglobe {{number_of_strips}} {{path/to/image.ppm}} > {{path/to/output.ppm}}`
+
+- Use the specified color for the areas between the strips:
+
+`ppmglobe -background {{red}} {{number_of_strips}} {{path/to/image.ppm}} > {{path/to/output.ppm}}`