Make optional props actually optional

[zpao]

This drops use of defaultProps in favor of inline destructuring with default assignment.

This should effectively be type compatible with the rest of 3.x (slightly different but close enough) and it prepares for an easier implementation of forwardRef (which will be in 4.0 since I don't want to support that and the default QRCode export)

Fixes #197

[zpao]

This would get better in a future version. I wanted behavior to remain the same in 3.x (always update) but in 4.x we'd use this as an input to useEffect

[zpao]

For posterity, this is the diff of the type declarations. You can see that there are only 2 notable differences:

1. Removal of the additional namespace for each component, which housed the defaultProps.
2. Some props being made optional.

While technically we could argue that the removal of the namespace is a breaking change and cause for a major version, I don't agree.

--- index.d.ts	2022-06-24 12:01:29.000000000 -0700
+++ lib/index.d.ts	2022-06-24 12:00:46.000000000 -0700
@@ -1,65 +1,38 @@
 import React, { CSSProperties } from 'react';
 
 /**
  * @license qrcode.react
  * Copyright (c) Paul O'Shannessy
  * SPDX-License-Identifier: ISC
  */
 
+declare type ImageSettings = {
+    src: string;
+    height: number;
+    width: number;
+    excavate: boolean;
+    x?: number;
+    y?: number;
+};
 declare type QRProps = {
     value: string;
-    size: number;
-    level: string;
-    bgColor: string;
-    fgColor: string;
+    size?: number;
+    level?: string;
+    bgColor?: string;
+    fgColor?: string;
     style?: CSSProperties;
-    includeMargin: boolean;
-    imageSettings?: {
-        src: string;
-        height: number;
-        width: number;
-        excavate: boolean;
-        x?: number;
-        y?: number;
-    };
+    includeMargin?: boolean;
+    imageSettings?: ImageSettings;
 };
 declare type QRPropsCanvas = QRProps & React.CanvasHTMLAttributes<HTMLCanvasElement>;
 declare type QRPropsSVG = QRProps & React.SVGProps<SVGSVGElement>;
 declare function QRCodeCanvas(props: QRPropsCanvas): JSX.Element;
-declare namespace QRCodeCanvas {
-    var defaultProps: {
-        size: number;
-        level: string;
-        bgColor: string;
-        fgColor: string;
-        includeMargin: boolean;
-    };
-}
 declare function QRCodeSVG(props: QRPropsSVG): JSX.Element;
-declare namespace QRCodeSVG {
-    var defaultProps: {
-        size: number;
-        level: string;
-        bgColor: string;
-        fgColor: string;
-        includeMargin: boolean;
-    };
-}
 declare type RootProps = (QRPropsSVG & {
     renderAs: 'svg';
 }) | (QRPropsCanvas & {
-    renderAs: 'canvas';
+    renderAs?: 'canvas';
 });
-declare const QRCode: {
-    (props: RootProps): JSX.Element;
-    defaultProps: {
-        size: number;
-        level: string;
-        bgColor: string;
-        fgColor: string;
-        includeMargin: boolean;
-        renderAs: string;
-    };
-};
+declare const QRCode: (props: RootProps) => JSX.Element;
 
 export { QRCodeCanvas, QRCodeSVG, QRCode as default };