feat(platforms): added platform support (#67)

Now libraries can be assigned to platforms in the admin section.
Games will be assigned to libraries on scanning.

Resolves grimsi/gameyfin#31

Co-authored-by: shawly <shawlyde@gmail.com>

frontend/src/app/models/dtos/PlatformDto.ts

@@ -0,0 +1,5 @@
+export class PlatformDto {
+  slug!: string;
+  name!: string;
+  platformLogoId?: string;
+}