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

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

pages/common/pamtowinicon.md

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+# pamtowinicon
+
+> Convert a PAM image to a Windows ICO file.
+> More information: <https://netpbm.sourceforge.net/doc/pamtowinicon.html>.
+
+- Convert a PAM image file to an ICO file:
+
+`pamtowinicon {{path/to/input_file.pam}} > {{path/to/output.ico}}`
+
+- Encode images with resolutions smaller than t in the BMP format and all other images in the PNG format:
+
+`pamtowinicon -pngthreshold {{t}} {{path/to/input_file.pam}} > {{path/to/output.ico}}`
+
+- Make all pixels outside the non-opaque area black:
+
+`pamtowinicon -truetransparent {{path/to/input_file.pam}} > {{path/to/output.ico}}`