Add notes to classes which don't inherit Class (#5878)

* Add note about LatLng not inheriting Class

Fixes #3301.

* Add note about LatLngBounds, Bounds, Point, CRSs and projections not inheriting Class

src/geo/LatLng.js

@@ -21,6 +21,10 @@ import {toLatLngBounds} from './LatLngBounds';
  * map.panTo({lat: 50, lng: 30});
  * map.panTo(L.latLng(50, 30));
  * ```
+ *
+ * Note that `LatLng` does not inherit from Leafet's `Class` object,
+ * which means new classes can't inherit from it, and new methods
+ * can't be added to it with the `include` function.
  */
 
 export function LatLng(lat, lng, alt) {

src/geo/LatLngBounds.js

@@ -24,6 +24,10 @@ import {LatLng, toLatLng} from './LatLng';
  * ```
  *
  * Caution: if the area crosses the antimeridian (often confused with the International Date Line), you must specify corners _outside_ the [-180, 180] degrees longitude range.
+ *
+ * Note that `LatLngBounds` does not inherit from Leafet's `Class` object,
+ * which means new classes can't inherit from it, and new methods
+ * can't be added to it with the `include` function.
  */
 
 export function LatLngBounds(corner1, corner2) { // (LatLng, LatLng) or (LatLng[])

src/geo/crs/CRS.js

@@ -15,6 +15,10 @@ import * as Util from '../../core/Util';
  * Leaflet defines the most usual CRSs by default. If you want to use a
  * CRS not defined by default, take a look at the
  * [Proj4Leaflet](https://github.com/kartena/Proj4Leaflet) plugin.
+ *
+ * Note that the CRS instances do not inherit from Leafet's `Class` object,
+ * and can't be instantiated. Also, new classes can't inherit from them, 
+ * and methods can't be added to them with the `include` function.
  */
 
 export var CRS = {

src/geo/projection/index.js

@@ -15,6 +15,10 @@
  * The inverse of `project`. Projects a 2D point into a geographical location.
  * Only accepts actual `L.Point` instances, not arrays.
 
+ * Note that the projection instances do not inherit from Leafet's `Class` object,
+ * and can't be instantiated. Also, new classes can't inherit from them, 
+ * and methods can't be added to them with the `include` function.
+
  */
 
 export {LonLat} from './Projection.LonLat';

src/geometry/Bounds.js

@@ -19,6 +19,10 @@ import {Point, toPoint} from './Point';
  * ```js
  * otherBounds.intersects([[10, 10], [40, 60]]);
  * ```
+ *
+ * Note that `Bounds` does not inherit from Leafet's `Class` object,
+ * which means new classes can't inherit from it, and new methods
+ * can't be added to it with the `include` function.
  */
 
 export function Bounds(a, b) {

src/geometry/Point.js

@@ -18,6 +18,10 @@ import {isArray, formatNum} from '../core/Util';
  * map.panBy([200, 300]);
  * map.panBy(L.point(200, 300));
  * ```
+ *
+ * Note that `Point` does not inherit from Leafet's `Class` object,
+ * which means new classes can't inherit from it, and new methods
+ * can't be added to it with the `include` function.
  */
 
 export function Point(x, y, round) {