Update cheatsheets

sputoppm

@@ -0,0 +1,13 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# sputoppm
+
+> Convert an Atari uncompressed Spectrum image to a PPM image.
+> More information: <https://netpbm.sourceforge.net/doc/sputoppm.html>.
+
+- Convert an SPU file to a PPM image:
+
+`sputoppm {{path/to/input.spu}} > {{path/to/output.ppm}}`