errno: add page (#7873)

pages/common/errno.md

@@ -0,0 +1,20 @@
+# errno
+
+> Look up errno names and descriptions.
+> More information: <https://joeyh.name/code/moreutils/>.
+
+- Lookup errno description by name or code:
+
+`errno {{name|code}}`
+
+- List all errno names, codes, and descriptions:
+
+`errno --list`
+
+- Search for code who's description contains all of the given text:
+
+`errno --search {{text}}`
+
+- Search for code who's description contains all of the given text (all locales):
+
+`errno --search-all-locales {{text}}`