fix corrupted part of descender and outline when using Bitmap#drawSmallText

[rutan]

Bitmap#drawSmallText has 2 problems 😭

---

(1)
bitmap.width is read only property.
so, bitmap.width *= 2 is not working.

corescript/js/rpg_core/Bitmap.js

Lines 328 to 343 in cbc82b3

	/**
	* [read-only] The width of the bitmap.
	*
	* @property width
	* @type Number
	*/
	Object.defineProperty(Bitmap.prototype, 'width', {
	get: function() {
	if(this.isReady()){
	return this._image? this._image.width: this._canvas.width;
	}
	return 0;
	},
	configurable: true
	});

(2)
Bitmap#drawSmallText cannot drawn outline (Bitmap#outlineWidth) or descender alphabet (ex. g, j, p ...)... 😱

---

I try fix these issues.
Please check this PR 🙏

[krmbn0576]

LGTM! 🍣

[Sigureya]

OK!

[rutan]

😊