chore: housekeeping — linter & formatter setup

Add .prettierrc.json, .markdownlint.json, .yamllint.yaml, .gitattributes
Run CSharpier, Prettier and markdownlint across the entire codebase.
No logic changes — formatting, using order and line endings only.

HellionChat/HellionChat.csproj

@@ -80,7 +80,6 @@
         </EmbeddedResource>
     </ItemGroup>
 
-
     <!-- Plugin icon. Copy images/* into the build output so Dalamud
          finds the icon next to the DLL, and let the SDK default
          DalamudPackager pipeline include the same path in the
@@ -94,5 +93,4 @@
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </None>
     </ItemGroup>
-
 </Project>