docs(linter): Add configuration docs to no-useless-escape lint rule. (#14791)

Also add missing text for "Why is this bad?" section. I've updated this
to use the autogen docs rather than an explicit Options section, since
that seems to be the preferred implementation path for this kind of
addition.

Part of #14743.

Results in:

```md
## Configuration

This rule accepts a configuration object with the following properties:

### allowRegexCharacters

type: `string[]`

default: `[]`

An array of characters that are allowed to be escaped unnecessarily in regexes.
```

---------

Signed-off-by: Connor Shea <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: connorshea

crates/oxc_linter/src/rules/eslint/no_useless_escape.rs

@@ -8,6 +8,7 @@ use oxc_regular_expression::{
 };
 use oxc_semantic::NodeId;
 use oxc_span::Span;
+use schemars::JsonSchema;
 
 use crate::{AstNode, context::LintContext, rule::Rule};
 
@@ -26,18 +27,23 @@ impl std::ops::Deref for NoUselessEscape {
     }
 }
 
-#[derive(Debug, Default, Clone)]
+#[derive(Debug, Default, Clone, JsonSchema)]
+#[serde(rename_all = "camelCase", default)]
 pub struct NoUselessEscapeConfig {
+    /// An array of characters that are allowed to be escaped unnecessarily in regexes.
     allow_regex_characters: Vec<char>,
 }
 
 declare_oxc_lint!(
     /// ### What it does
     ///
-    /// Disallow unnecessary escape characters
+    /// Disallow unnecessary escape characters.
     ///
     /// ### Why is this bad?
     ///
+    /// Escaping characters unnecessarily has no effect on the behavior of strings or regexes,
+    /// and can make code harder to read and understand by adding unnecessary complexity.
+    /// This applies to string literals, template literals, and regular expressions.
     ///
     /// ### Examples
     ///
@@ -81,7 +87,8 @@ declare_oxc_lint!(
     NoUselessEscape,
     eslint,
     correctness,
-    fix
+    fix,
+    config = NoUselessEscapeConfig,
 );
 
 impl Rule for NoUselessEscape {