pnmtorast, pnmtorle, pnmtosgi, pnmtosir, rasttopnm, rletopnm, sgitopnm, sirtopnm: add pages (#11410)

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

pages/common/pnmtorle.md

@@ -0,0 +1,16 @@
+# pnmtorle
+
+> Convert a PNM file to an Utah Raster Tools RLE image file.
+> More information: <https://netpbm.sourceforge.net/doc/pnmtorle.html>.
+
+- Convert a PNM image to an RLE image:
+
+`pnmtorle {{path/to/input.pnm}} > {{path/to/output.rle}}`
+
+- Print PNM header information to `stdout`:
+
+`pnmtorle -verbose {{path/to/input.pnm}} > {{path/to/output.rle}}`
+
+- Include a transparency channel in the output image in which every black pixel is set to fully transparent and every other pixel is set to fully opaque:
+
+`pnmtorle -alpha {{path/to/input.pnm}} > {{path/to/output.rle}}`