feat: Camera should allow for additional `accept` types for file selection

[baffioso]

ionic/pwa-elements version:

@ionic/pwa-elements@3.0.2

I'm submitting a ... (check one with "x")
[ ] bug report
[x] feature request

Current behavior:
At the moment accept="image/*" is hard coded as accepted input types, when users choose to select a local file/file from disk.

Expected behavior:
Enable configuration of PWA camera for specifying accepted input types e.g. accept="image/png,image/jpeg"

Related code:

pwa-elements/src/components/camera/camera.tsx

Lines 466 to 471 in 6e1394a

	<input
	type="file"
	id="_pwa-elements-file-pick"
	onChange={this.handleFileInputChange}
	accept="image/*"
	class="pick-image-button" />

Other information:
https://forum.ionicframework.com/t/restrict-file-types-in-pwa-camera-from-ionic-pwa-elements-when-selecting-local-image/208222