Update README documentation

Author: tlikonen

README.md

@@ -139,7 +139,7 @@ be used to read option's name from the condition object.
 ### Condition: `unknown-option`
 
 `getopt` function may signal this condition when it finds an unknown
-condition. Function `option-name` can be used to read option's name from
+option. Function `option-name` can be used to read option's name from
 the condition object.