fix: add typing doc

Author: HerringtonDarkholme

website/guide/pattern-syntax.md

@@ -10,7 +10,6 @@ through the full syntax tree, so pattern can also match nested expression. For e
 code.
 
 ```javascript
-
 const b = a + 1
 
 funcCall(a + 1)

website/reference/api.md

@@ -117,6 +117,10 @@ class SgNode {
   isNamed(): boolean
   isNamedLeaf(): boolean
   kind(): string
+  // check if node has kind
+  is(kind: string): boolean
+  // for TypeScript type narrow
+  kindToRefine: string
   text(): string
   // Check if node meets certain patterns
   matches(m: string): boolean
@@ -147,6 +151,8 @@ class SgNode {
 }
 ```
 
+Some methods have more sophisticated type signature for the ease of use. See the [source code](https://github.com/ast-grep/ast-grep/blob/0999cdb542ff4431e3734dad38fcd648de972e6a/crates/napi/types/sgnode.d.ts#L38-L41) and our [tech blog](/blog/typed-napi.html)
+
 ### NapiConfig
 
 `NapiConfig` is used in `find` or `findAll`.