Guides for Serilog and EFCore (#2134)

* Add serilog guide

* added suggestions from Rozen

* Add efcore guide

* Fix review changes

* Fix grammatical errors & review points

docs/guides/other_libs/samples/InteractionModuleDISample.cs

@@ -0,0 +1,20 @@
+using Discord;
+
+public class SampleModule : InteractionModuleBase<SocketInteractionContext>
+{
+    private readonly ApplicationDbContext _db;
+
+    public SampleModule(ApplicationDbContext db)
+    {
+        _db = db;
+    }
+
+    [SlashCommand("sample", "sample")]
+    public async Task Sample()
+    {
+        // Do stuff with your injected DbContext
+        var user = _db.Users.FirstOrDefault(x => x.Id == Context.User.Id);
+
+        ...
+  }
+}