Merge 'bindings/javascript: Add database property to Statement' from Anton Harniakou

Implements `.database` property on Statement object.
```js
let stmt = db.prepare("SELECT 1");
stmt.database == db // will return the database object the stmt was create with
```

Reviewed-by: Diego Reis (@el-yawd)

Closes #1671

bindings/javascript/__test__/better-sqlite3.spec.mjs

@@ -95,6 +95,12 @@ test("Test exec()", async (t) => {
   }
 });
 
+test("Test Statement.database gets the database object", async t => {
+  const [db] = await connect(":memory:");
+  let stmt = db.prepare("SELECT 1");
+  t.is(stmt.database, db);
+});
+
 
 const connect = async (path) => {
   const db = new Database(path);

bindings/javascript/__test__/limbo.spec.mjs

@@ -155,6 +155,12 @@ test("Test exec()", async (t) => {
   }
 });
 
+test("Test Statement.database gets the database object", async t => {
+  const [db] = await connect(":memory:");
+  let stmt = db.prepare("SELECT 1");
+  t.is(stmt.database, db);
+});
+
 const connect = async (path) => {
   const db = new Database(path);
   return [db];

bindings/javascript/wrapper.js

@@ -32,7 +32,7 @@ class Database {
    */
   prepare(sql) {
     try {
-      return new Statement(this.db.prepare(sql));
+      return new Statement(this.db.prepare(sql), this);
     } catch (err) {
       throw convertError(err);
     }
@@ -148,8 +148,9 @@ class Database {
  * Statement represents a prepared SQL statement that can be executed.
  */
 class Statement {
-  constructor(stmt) {
+  constructor(stmt, database) {
     this.stmt = stmt;
+    this.db = database;
   }
 
   /**
@@ -176,6 +177,10 @@ class Statement {
     throw new Error("not implemented");
   }
 
+  get database() {
+    return this.db;
+  }
+
   /**
    * Executes the SQL statement and returns an info object.
    */