(lint/types): explicit return types for all functions

- reuse React.Component types where possible, just like with the
  SignaturePad types

src/index.tsx

@@ -33,29 +33,29 @@ export class SignatureCanvas extends Component<SignatureCanvasProps> {
  _sigPad: SignaturePad = {} as SignaturePad
  _canvas: HTMLCanvasElement = {} as HTMLCanvasElement
 
- private readonly setRef = (ref: HTMLCanvasElement | null) => {
+ private readonly setRef = (ref: HTMLCanvasElement | null): void => {
  if (ref) {
  this._canvas = ref
  }
  }
 
- _excludeOurProps = () => {
+ _excludeOurProps = (): SignaturePad.SignaturePadOptions => {
  const { canvasProps, clearOnResize, ...sigPadProps } = this.props
  return sigPadProps
  }
 
- componentDidMount () {
+ componentDidMount: Component['componentDidMount'] = () => {
  this._sigPad = new SignaturePad(this._canvas, this._excludeOurProps())
  this._resizeCanvas()
  this.on()
  }
 
- componentWillUnmount () {
+ componentWillUnmount: Component['componentWillUnmount'] = () => {
  this.off()
  }
 
  // propagate prop updates to SignaturePad
- componentDidUpdate () {
+ componentDidUpdate: Component['componentDidUpdate'] = () => {
  Object.assign(this._sigPad, this._excludeOurProps())
  }
 
@@ -80,14 +80,14 @@ export class SignatureCanvas extends Component<SignatureCanvasProps> {
  return this._sigPad
  }
 
- _checkClearOnResize = () => {
+ _checkClearOnResize = (): void => {
  if (!this.props.clearOnResize) {
  return
  }
  this._resizeCanvas()
  }
 
- _resizeCanvas = () => {
+ _resizeCanvas = (): void => {
  const canvasProps = this.props.canvasProps || {}
  const { width, height } = canvasProps
  // don't resize if the canvas has fixed width and height
@@ -111,7 +111,7 @@ export class SignatureCanvas extends Component<SignatureCanvasProps> {
  this.clear()
  }
 
- render () {
+ render: Component['render'] = () => {
  const { canvasProps } = this.props
  return <canvas ref={this.setRef} {...canvasProps} />
  }