palmtopnm: add page (#11057)

* palmtopnm: add page

* Update pages/common/palmtopnm.md

Co-authored-by: Juri Dispan <juri.dispan@posteo.net>

---------

Co-authored-by: Juri Dispan <juri.dispan@posteo.net>

pages/common/palmtopnm.md

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+# palmtopnm
+
+> Convert a Palm Bitmap file to a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/palmtopnm.html>.
+
+- Generate the PNM image as output, for a Palm Bitmap file as input:
+
+`palmtopnm {{path/to/file.palm}}`
+
+- Display various information about the input Palm Bitmap file and process:
+
+`palmtopnm -verbose {{path/to/file.palm}}`
+
+- Generate a histogram of colours in the input Palm Bitmap file to `stderr`:
+
+`palmtopnm -showhist {{path/to/file.palm}}`
+
+- Display version:
+
+`palmtopnm -version`