pamflip, pnmcolormap, pnmquant, pnmremap, pnmrotate, ppmquant: add pages (#11800)

* pamflip, pnmcolormap, pnmquant, pnmremap, pnmrotate, ppmquant: add pages

---------

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/pnmremap.md

@@ -0,0 +1,20 @@
+# pnmremap
+
+> Replace the colors in a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pnmremap.html>.
+
+- Replace the colors in an image with those in the specified color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Use Floyd-Steinberg dithering for representing colors missing in the color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} -floyd {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Use the first color in the palette for representing colors missing in the color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} -firstisdefault {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Use the specified color for representing colors missing in the color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} -missingcolor {{color}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`