cjxl, djxl: move to common (#13621)

pages/common/djxl.md

@@ -0,0 +1,13 @@
+# djxl
+
+> Decompress JPEG XL images.
+> Accepted output extensions are PNG, APNG, JPEG, EXR, PGM, PPM, PNM, PFM, PAM, EXIF, XMP and JUMBF.
+> More information: <https://github.com/libjxl/libjxl>.
+
+- Decompress a JPEG XL image to another format:
+
+`djxl {{path/to/image.jxl}} {{path/to/output.ext}}`
+
+- Display an extremely detailed help page:
+
+`djxl --help --verbose --verbose --verbose --verbose`