fix: add unknown package manager callback (#6)

* fix: add unknown package manager callback

* chore: update unknown pm callback hint

* chore: rename callback

src/index.ts

@@ -7,12 +7,18 @@ import { AGENTS, LOCKS } from './agents'
 
 export interface DetectOptions {
   cwd?: string
+  /**
+   * Callback when unknown package manager from package.json.
+   *
+   * @param packageManager - The `packageManager` value from package.json file.
+   */
+  onUnknown?: (packageManager: string) => void
 }
 
 export type { Agent }
 export { AGENTS, LOCKS }
 
-export async function detect({ cwd }: DetectOptions = {}) {
+export async function detect({ cwd, onUnknown }: DetectOptions = {}) {
   let agent: Agent | undefined
   let version: string | undefined
 
@@ -42,6 +48,9 @@ export async function detect({ cwd }: DetectOptions = {}) {
         else if (AGENTS.includes(name)) {
           agent = name
         }
+        else {
+          onUnknown?.(pkg.packageManager)
+        }
       }
     }
     catch {}