feat(deps): upgrade to Angular v9 (#73)

BREAKING CHANGE: ngx-translate http-loader is now built for Angular 9, if you use Angular 8 or below please refer to the [compatibility table](https://github.com/ngx-translate/http-loader/blob/v4.0.0/ngx-translate/http-loader#installation) to know which version you can install

Author: damingerdai

README.md

@@ -23,6 +23,8 @@ Choose the version corresponding to your Angular version:
 
  Angular     | @ngx-translate/core | @ngx-translate/http-loader
  ----------- | ------------------- | --------------------------
+ 9           | 12.x+               | 5.x+
+ 8           | 12.x+               | 4.x+
  7           | 11.x+               | 4.x+
  6           | 10.x                | 3.x
  5           | 8.x to 9.x          | 1.x to 2.x

angular.json

@@ -14,6 +14,11 @@
           "options": {
             "tsConfig": "projects/ngx-translate/http-loader/tsconfig.lib.json",
             "project": "projects/ngx-translate/http-loader/ng-package.json"
+          },
+          "configurations": {
+            "production": {
+              "tsConfig": "projects/ngx-translate/http-loader/tsconfig.lib.prod.json"
+            }
           }
         },
         "test": {