pamtowinicon, pgmtosbig, pgmtost4, ppmtowinicon, sbigtopgm, st4topgm, winicontopam, winicontoppm: add pages (#11404)

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

pages/common/winicontopam.md

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+# winicontopam
+
+> Convert a Windows ICO file to a PAM file.
+> More information: <https://netpbm.sourceforge.net/doc/winicontopam.html>.
+
+- Read an ICO file and convert the best quality image contained therein to the PAM format:
+
+`winicontopam {{path/to/input_file.ico}} > {{path/to/output.pam}}`
+
+- Convert all images in the input file to PAM:
+
+`winicontopam -allimages {{path/to/input_file.ico}} > {{path/to/output.pam}}`
+
+- Convert the n'th image in the input file to PAM:
+
+`winicontopam -image {{n}} {{path/to/input_file.ico}} > {{path/to/output.pam}}`
+
+- If the image(s) to be extracted contain graded transparency data and an AND mask, write the AND mask into the fifth channel of the output PAM file:
+
+`winicontopam -andmasks {{path/to/input_file.ico}} > {{path/to/output.pam}}`