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

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

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

pages/common/pnmrotate.md

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+# pnmrotate
+
+> Rotate a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pnmrotate.html>.
+
+- Rotate a PNM image by some angle (measured in degrees, counter-clockwise):
+
+`pnmrotate {{angle}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Specify the background color exposed by rotating the input image:
+
+`pnmrotate -background {{color}} {{angle}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Disable anti-aliasing, improving performance but decreasing quality:
+
+`pnmrotate -noantialias {{angle}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`