add description about specifying multiple errors using directives

Ignore.md

@@ -19,6 +19,11 @@ Use a `-e` flag to disable a specific error when running shellcheck:
 
 ### Ignoring one or more type of error forever
 
+You can pass multiple errors to [[directive]]:
+
+    # shellcheck disable=SC2116,SC2086
+    hash=$(echo ${hash})    # trim spaces
+
 In v0.7.0 you can create a file `.shellcheckrc` in your home directory (or your project's base directory), and add `disable` directives to it:
 
     $ cat ~/.shellcheckrc