Export VS Code Design System (#292)

Description of changes

Fix a bug where the contents of `src/vscode-design-system.ts` and `src/custom-elements.ts` were not being exported by the package.

Also rename `FASTDesignSystem` to `VSCodeDesignSystem` in `src/index-rollup.ts`.

Author: hawkticehurst

src/index-rollup.ts

@@ -12,5 +12,5 @@ export * from './index';
  * Only available if the components are added through a script tag
  * rather than a module/build system.
  */
-export const FASTDesignSystem =
+export const VSCodeDesignSystem =
 	provideVSCodeDesignSystem().register(allComponents);

src/index.ts

@@ -1,6 +1,9 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+export * from './vscode-design-system';
+export * from './custom-elements';
+
 // Export components and classes
 export * from './badge/index';
 export * from './button/index';