fix(file): readAsText() and adds readAsDataURL() in File plugin (#346)

* Updates docs for CameraPreview, Base64ToGallery and Developer.MD

-DEVELOPER.md: Corrects 'npm run tslint' instruction to 'npm run lint'
-CameraPreview: Fixes syntax error in hide
-Base64ToGallery: Adds desc of options obj props

* Fixes resolveLocalFileSystemURL bug in File.readAsText() and adds File.readAsDataUrl()

- File.readAsText(): window.resolveLocalFileSystemURL() was incorrectly implemented

* Updates callback arg in File.checkFile()

Callback arg of window.resolveLocalFileSystemURL was fileSystem, but it actually returns fileEntry

* Corrects repo link and comments out setFlashMode()

- Repo prop and link in desc were not pointing to the same gh repo as the plugin
- setFlashMode() is not currently available in the repo that gets pulled by the corodova plugin

src/plugins/camera-preview.ts

@@ -33,13 +33,13 @@ export interface CameraPreviewSize {
  * @description
  * Showing camera preview in HTML
  *
- * Requires {@link module:driftyco/ionic-native} and the Cordova plugin: `cordova-plugin-camera-preview`. For more info, please see the [Cordova Camera Preview Plugin Docs](https://github.com/westonganger/cordova-plugin-camera-preview).
+ * Requires {@link module:driftyco/ionic-native} and the Cordova plugin: `cordova-plugin-camera-preview`. For more info, please see the [Cordova Camera Preview Plugin Docs](https://github.com/cordova-plugin-camera-preview/cordova-plugin-camera-preview).
  *
  */
 @Plugin({
   plugin: 'cordova-plugin-camera-preview',
   pluginRef: 'cordova.plugins.camerapreview',
-  repo: 'https://github.com/westonganger/cordova-plugin-camera-preview',
+  repo: 'https://github.com/cordova-plugin-camera-preview/cordova-plugin-camera-preview',
   platforms: ['Android', 'iOS']
 })
 export class CameraPreview {
@@ -104,10 +104,10 @@ export class CameraPreview {
   /**
    * Set the default mode for the Flash.
    */
-  @Cordova({
-    sync: true
-  })
-  static setFlashMode(mode: number): void { };
+  // @Cordova({
+  //   sync: true
+  // })
+  // static setFlashMode(mode: number): void { };
 
   /**
    * Set camera color effect.