docs: Add clarification about eslint-enable (#15680)

* docs: Add clarification about eslint-enable rule:

Fixes #15662

* Update docs/user-guide/configuring/rules.md

* Update docs/user-guide/configuring/rules.md

Co-authored-by: Nicholas C. Zakas <nicholas@humanwhocodes.com>
Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com>

docs/user-guide/configuring/rules.md

@@ -144,6 +144,8 @@ console.log('bar');
 /* eslint-enable no-alert, no-console */
 ```
 
+**Note:** `/* eslint-enable */` without any specific rules listed will cause all disabled rules to be re-enabled.
+
 To disable rule warnings in an entire file, put a `/* eslint-disable */` block comment at the top of the file:
 
 ```js
@@ -160,6 +162,14 @@ You can also disable or enable specific rules for an entire file:
 alert('foo');
 ```
 
+To ensure that a rule is never applied (regardless of any future enable/disable lines):
+
+```js
+/* eslint no-alert: "off" */
+
+alert('foo');
+```
+
 To disable all rules on a specific line, use a line or block comment in one of the following formats:
 
 ```js