chore: update StackBlitz links (#1254)

Author: CaerusKaru

.github/ISSUE_TEMPLATE/Bug.md

@@ -13,7 +13,7 @@ about: Something is broken in Angular Layout
 #### What are the steps to reproduce?
 Providing a StackBlitz (or similar) is the *best* way to get the team to see your issue.
 
-*  [StackBlitz starter](https://goo.gl/y38GUZ) using latest `npm` nightly release: 
+*  [StackBlitz starter](https://stackblitz.com/edit/flex-layout-seed-nightly) using latest `npm` nightly release: 
 
 
 #### What is the use-case or motivation for changing an existing behavior?

CONTRIBUTING.md

@@ -240,5 +240,5 @@ changes to be accepted, the CLA must be signed. It's a quick process, we promise
 [gitter]: https://gitter.im/angular/flex-layout
 [individual-cla]: http://code.google.com/legal/individual-cla-v1.0.html
 [js-style-guide]: https://google.github.io/styleguide/jsguide.html
-[stackblitz]: https://stackblitz.com/edit/angular-flex-layout-seed
+[stackblitz]: https://stackblitz.com/edit/flex-layout-seed
 [stackoverflow]: http://stackoverflow.com/

README.md

@@ -61,8 +61,8 @@ Check out [all of the available options](https://github.com/angular/flex-layout/
 
 ### StackBlitz Templates
 
-  *  [Flex-Layout Template](https://stackblitz.com/edit/angular-flex-layout-seed?file=app%2Fapp.component.ts)
-  *  [Flex-Layout + Material](https://stackblitz.com/edit/angular-material-flex-layout-seed?file=app%2Fapp.module.ts)
+  *  [Flex-Layout Template](https://stackblitz.com/edit/flex-layout-seed)
+  *  [Flex-Layout + Material](https://stackblitz.com/edit/flex-layout-material-seed)
 
 ### Developers