docs: Move 'Events' to design docs

Signed-off-by: David Mehren <git@herrmehren.de>

docs/content/dev/design_docs/events.md

@@ -1,8 +1,12 @@
-In HedgeDoc we use an event system based on [EventEmitter2][eventemitter2]. It's used to reduce circular dependencies between different services and inform these services about changes.
+# Events
+
+In HedgeDoc 2, we use an event system based on [EventEmitter2][eventemitter2].
+It's used to reduce circular dependencies between different services and inform these services about changes.
 
 HedgeDoc's system is basically [the system NestJS offers][nestjs/eventemitter].  
 The config for the `EventEmitterModule` is stored in `events.ts` and exported as `eventModuleConfig`.  
-In the same file enums for the event keys are defined. Each of these events is expected to be sent with an additional value. In the enum defintion a comment should tell you what exactly this value should be.
+In the same file enums for the event keys are defined. Each of these events is expected to be sent with an additional value.
+In the enum definition a comment should tell you what exactly this value should be.
 
 [eventemitter2]: https://github.com/EventEmitter2/EventEmitter2
 [nestjs/eventemitter]: https://docs.nestjs.com/techniques/events

docs/mkdocs.yml

@@ -23,6 +23,7 @@ nav:
     - '2.0 Development': dev/2.0.md
     - Design Documents:
       - API Authentication: dev/design_docs/api_auth.md
+      - Events: dev/design_docs/events.md
       - Notes: dev/design_docs/notes.md
       - 'User Profiles & Authentication': dev/design_docs/user_profiles.md
       - Configuration: dev/design_docs/config.md