docs(message_length_limit): document non-negative limit

Author: ttw225

docs/config/check.md

@@ -22,6 +22,7 @@ List of prefixes that commitizen ignores when verifying messages.
 - Default: `0` (no limit)
 
 Maximum length of the commit message. Setting it to `0` disables the length limit.
+This value must be a non-negative integer (`>= 0`).
 
 !!! note
     This option can be overridden by the `-l/--message-length-limit` command line argument.

docs/config/commit.md

@@ -24,3 +24,14 @@ Sets the character encoding to be used when parsing commit messages.
 - Default: `False`
 
 Retries failed commit when running `cz commit`.
+
+## `message_length_limit`
+
+- Type: `int`
+- Default: `0` (no limit)
+
+Maximum length of the commit message. Setting it to `0` disables the length limit.
+This value must be a non-negative integer (`>= 0`).
+
+!!! note
+    This option can be overridden by the `-l/--message-length-limit` command line argument.