added oneshot callback (trigger, then stop) when location is found

.gitignore

@@ -1,3 +1,6 @@
 .sass-cache
 bower_components/*
 node_modules/*
+.vscode
+.DS_Store
+

README.md

@@ -36,7 +36,7 @@ The control is [available from JsDelivr CDN](https://www.jsdelivr.com/projects/l
 
 #### Add the JavaScript and CSS files
 
-Then include the CSS and JavaScript files. 
+Then include the CSS and JavaScript files.
 
 ##### With CDN
 
@@ -78,6 +78,7 @@ Possible options are listed in the following table. More details are [in the cod
 <!-- prettier-ignore-start -->
 | Option     | Type      | Description       |  Default |
 |------------|-----------|-------------------|----------|
+| `oneshot_callback` | `function`  | function([lat,lng]) to be called *only once* when location is found. if this is set, `stop()` is called automatically when a location is first found. | `null` |
 | `position` | `string`  | Position of the control | `topleft` |
 | `layer` | [`ILayer`](http://leafletjs.com/reference.html#ilayer)  | The layer that the user's location should be drawn on. | a new layer |
 | `setView` | `boolean`  or `string`  | Set the map view (zoom and pan) to the user's location as it updates. Options are `false`, `'once'`, `'always'`, `'untilPan'`, or `'untilPanOrZoom'` | `'untilPanOrZoom'` |

src/L.Control.Locate.js

@@ -153,6 +153,9 @@ You can find the project at: https://github.com/domoritz/leaflet-locatecontrol
 
   const LocateControl = L.Control.extend({
     options: {
+      /** function([lat,lng]) to be called when location is found.
+      if this is set, stop() is called when location is first found. */
+      callback: null,
       /** Position of the control */
       position: "topleft",
       /** The layer that the user's location should be drawn on. By default creates a new layer. */
@@ -347,6 +350,11 @@ You can find the project at: https://github.com/domoritz/leaflet-locatecontrol
         }
       }
 
+      this._loc_callback=null
+      if (options.oneshot_callback) {
+        this._loc_callback=options.oneshot_callback
+      }
+
       // extend the follow marker style and circle from the normal style
       this.options.followMarkerStyle = L.extend({}, this.options.markerStyle, this.options.followMarkerStyle);
       this.options.followCircleStyle = L.extend({}, this.options.circleStyle, this.options.followCircleStyle);
@@ -768,9 +776,12 @@ You can find the project at: https://github.com/domoritz/leaflet-locatecontrol
       }
 
       this._event = e;
-
       this._drawMarker();
       this._updateContainerStyle();
+      if (this._loc_callback && this._active) {
+        // call the location callback
+        this._loc_callback(e.latlng)
+      }
 
       switch (this.options.setView) {
         case "once":
@@ -797,6 +808,10 @@ You can find the project at: https://github.com/domoritz/leaflet-locatecontrol
       }
 
       this._justClicked = false;
+      if (this.callback && !this.options.flyTo) {
+        this.stop()
+      }
+
     },
 
     /**
@@ -839,6 +854,10 @@ You can find the project at: https://github.com/domoritz/leaflet-locatecontrol
           this._drawMarker();
         }
       }
+
+      if (this._loc_callback) {
+        this.stop()
+      }
     },
 
     /**