docs(angular.merge): add notes about support and lodash compatibility

Closes #16187
Closes #14512

Author: Narretz

src/Angular.js

@@ -396,8 +396,8 @@ function extend(dst) {
 * sinceVersion="1.6.5"
 * This function is deprecated, but will not be removed in the 1.x lifecycle.
 * There are edge cases (see {@link angular.merge#known-issues known issues}) that are not
-* supported by this function. We suggest
-* using [lodash's merge()](https://lodash.com/docs/4.17.4#merge) instead.
+* supported by this function. We suggest using another, similar library for all-purpose merging,
+* such as [lodash's merge()](https://lodash.com/docs/4.17.4#merge).
 *
 * @knownIssue
 * This is a list of (known) object types that are not handled correctly by this function:
@@ -406,6 +406,8 @@ function extend(dst) {
 * - [`CanvasGradient`](https://developer.mozilla.org/docs/Web/API/CanvasGradient)
 * - AngularJS {@link $rootScope.Scope scopes};
 *
+* `angular.merge` also does not support merging objects with circular references.
+*
 * @param {Object} dst Destination object.
 * @param {...Object} src Source object(s).
 * @returns {Object} Reference to `dst`.