pamnoraw, pamtopam, pamtopnm, pnmtoplainpnm, pnmtopnm, ppmtoppm: add pages (#11403)

* pamnoraw, pamtopam, pamtopnm, pnmtoplainpnm, pnmtopnm, ppmtoppm: add pages

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Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/common/pamtopnm.md

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+# pamtopnm
+
+> Convert a PAM image to an equivalent PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pamtopnm.html>.
+
+- Convert a PAM image to an equivalent PNM image, i.e. a PBM, PGM or PPM image:
+
+`pamtopnm {{path/to/image.pam}} > {{path/to/output.pbm|pgm|ppm}}`
+
+- Display version:
+
+`pamtopnm -version`