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/pamflip.md

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+# pamflip
+
+> Flip or rotate a PAM or PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pamflip.html>.
+
+- Rotate the input image counter-clockwise for a specific degree:
+
+`pamflip -rotate{{90|180|270}} {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Flip left for right:
+
+`pamflip -leftright {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Flip top for bottom:
+
+`pamflip -topbottom {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Flip the input image on the main diagonal:
+
+`pamflip -transpose {{path/to/input.pam}} > {{path/to/output.pam}}`