pbmtogem: add page (#11343)

* added /common/pages/pbmtogem.md

* Update pages/common/pbmtogem.md

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

---------

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

pages/common/pbmtogem.md

@@ -0,0 +1,17 @@
+# pbmtogem
+
+> Read a PBM image as input and produce a compressed GEM .img file as output.
+> `pbmtogem` cannot compress repeated lines.
+> More information: <https://netpbm.sourceforge.net/doc/pbmtogem.html>.
+
+- Convert a PBM image into a GEM .img file:
+
+`pbmtogem {{path/to/file.pbm}} > {{path/to/file.img}}`
+
+- Suppress all informational messages:
+
+`pbmtogem -quiet`
+
+- Display version:
+
+`pbmtogem -version`