document the need for finalizing prepared statements before closing the database

Author: gms1

docs/API.md

@@ -375,6 +375,10 @@ stmt.each([params...], callback, [complete]);
 
 Finalizes the prepared statement, freeing resources.
 
+> **Important:** You MUST finalize all prepared statements before closing the database.
+> If you attempt to close a database with unfinalized statements, you will get:
+> `SQLITE_BUSY: unable to close due to unfinalised statements`
+
 ```javascript
 stmt.finalize([callback]);
 ```
@@ -762,6 +766,10 @@ const count = await stmt.each([params], callback);
 
 Finalizes the statement.
 
+> **Important:** You MUST finalize all prepared statements before closing the database.
+> If you attempt to close a database with unfinalized statements, you will get:
+> `SQLITE_BUSY: unable to close due to unfinalised statements`
+
 ```javascript
 await stmt.finalize();
 ```

lib/promise/statement.js

@@ -60,6 +60,10 @@ class SqliteStatement {
     /**
    * Finalizes a prepared statement (freeing any resource used by this statement)
    *
+   * IMPORTANT: You MUST finalize all prepared statements before closing the database.
+   * If you attempt to close a database with unfinalized statements, you will get:
+   * SQLITE_BUSY: unable to close due to unfinalised statements
+   *
    * @returns {Promise<void>}
    */
     finalize() {

lib/sqlite3.d.ts

@@ -315,6 +315,11 @@ export class SqliteStatement {
         callback?: (err: Error | null, row: T) => void,
     ): Promise<number>;
 
+    /**
+     * Finalizes the statement.
+     * IMPORTANT: You MUST finalize all prepared statements before closing the database.
+     * Otherwise you will get SQLITE_BUSY: unable to close due to unfinalised statements
+     */
     finalize(): Promise<void>;
 }