Add multi-language AST-pattern scanning support

- Introduced `patterns` module with language-specific vulnerability patterns.
- Added `query_cache` utility for caching compiled queries.
- Expanded `scan.rs` to support scanning multiple languages dynamically.
- Updated `Cargo.toml` with additional tree-sitter dependencies.
- Added severity filtering to `ScannerConfig` for better configuration.

src/patterns/javascript.rs

@@ -0,0 +1,40 @@
+use crate::patterns::{Pattern, Severity};
+
+pub const PATTERNS: &[Pattern] = &[
+  Pattern {
+    id: "eval_call",
+    description: "Use of eval()",
+    query: "(call_expression function: (identifier) @id (#eq? @id \"eval\")) @vuln",
+    severity: Severity::High,
+  },
+  Pattern {
+    id: "new_function",
+    description: "new Function() constructor",
+    query: "(new_expression constructor: (identifier) @id (#eq? @id \"Function\")) @vuln",
+    severity: Severity::High,
+  },
+  Pattern {
+    id: "document_write",
+    description: "document.write() call",
+    query: "(call_expression function: (member_expression object: (identifier) @obj (#eq? @obj \"document\") property: (property_identifier) @prop (#eq? @prop \"write\"))) @vuln",
+    severity: Severity::Medium,
+  },
+  Pattern {
+    id: "inner_html_assignment",
+    description: "Assignment to element.innerHTML",
+    query: "(assignment_expression left: (member_expression property: (property_identifier) @prop (#eq? @prop \"innerHTML\"))) @vuln",
+    severity: Severity::Medium,
+  },
+  Pattern {
+    id: "settimeout_string",
+    description: "setTimeout / setInterval with a string argument",
+    query: "(call_expression function: (identifier) @id (#match? @id \"setTimeout|setInterval\") arguments: (arguments (string) @code . _)) @vuln",
+    severity: Severity::Medium,
+  },
+  Pattern {
+    id: "json_parse",
+    description: "JSON.parse on dynamic string",
+    query: "(call_expression function: (member_expression object: (identifier) @obj (#eq? @obj \"JSON\") property: (property_identifier) @prop (#eq? @prop \"parse\"))) @vuln",
+    severity: Severity::Low,
+  },
+];