contrib-guide.md: add info about warning/error blocks

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>

diff --git a/contrib-guide.md b/contrib-guide.md
index 5ae90797f85a603b33272795c9ff54fd1354ac1f..38366843d0fa5e60cdc0cab452a85bf9f2d4ff79 100644 (file)
--- a/contrib-guide.md
+++ b/contrib-guide.md
@@ -88,8 +88,11 @@ Tip/note block:
 </div>
 ```
 
-Title should be `Tip:` for a tip and `Note:` for a note.
+Replace the `tip` class with `warn` for a warning block, and with `err`
+for an error message block (when JavaScript is needed but is disabled, etc.).
 
+Title should be `Tip:` for a tip, `Note:` for a note, `Warning:` for a
+warning, and `Error:` for an error.
 
 
 #### External links