[Feature] Expose GetCurrentUser method & missing current user API methods (#2574)

* add stuff

* forgot to push

* docs

* Update DiscordRestClient.cs

* Apply suggestions from code review

* Update toc.yml

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Co-authored-by: Casmir <68127614+csmir@users.noreply.github.com>

docs/guides/toc.yml

@@ -126,6 +126,8 @@
       topicUid: Guides.OtherLibs.MediatR
 - name: Emoji
   topicUid: Guides.Emoji
+- name: Bearer Tokens
+  topicUid: Guides.BearerToken
 - name: Voice
   topicUid: Guides.Voice.SendingVoice
 - name: Deployment