Add info about autoupdater and file deletions to the HowToUpdate.md (CnCNet#852)

* Update HowToUpdate.md to mention `updateexec`

* Apply suggestion from @Metadorius

---------

Co-authored-by: Kerbiter <[email protected]>

Author: MahBoiDeveloper

Docs/HowToUpdate.md

@@ -19,6 +19,27 @@ This guide outlines the steps for updating the XNA CnCNet Client version for any
    - Unarchive `Resources` folder from `[xna-cncnet-client-X.Y.Z.7z]` file downloaded earlier inside the "game root" folder.
    - You **must** get a prompt to replace `Resources/` folder and files inside it. If not, you're in the wrong directory.
 
+> [!WARNING]
+> If you are using our automatic updater, make sure to check the release notes for any files that need to be added to the `[Delete]` section of `updateexec` or `preupdateexec`. Each release may specify the exact files that must be removed to prevent issues during the update process. For example (from release [2.12.12](https://github.com/CnCNet/xna-cncnet-client/releases/tag/2.12.12)):
+> ```ini
+> [Delete]
+> ; append those lines in the section
+> Resources\Binaries\Windows\DTAConfig.dll
+> Resources\Binaries\Windows\DTAConfig.pdb
+> Resources\Binaries\OpenGL\DTAConfig.dll
+> Resources\Binaries\OpenGL\DTAConfig.pdb
+> Resources\Binaries\XNA\DTAConfig.dll
+> Resources\Binaries\XNA\DTAConfig.pdb
+> Resources\BinariesNET8\Windows\DTAConfig.dll
+> Resources\BinariesNET8\Windows\DTAConfig.pdb
+> Resources\BinariesNET8\OpenGL\DTAConfig.dll
+> Resources\BinariesNET8\OpenGL\DTAConfig.pdb
+> Resources\BinariesNET8\UniversalGL\DTAConfig.dll
+> Resources\BinariesNET8\UniversalGL\DTAConfig.pdb
+> Resources\BinariesNET8\XNA\DTAConfig.dll
+> Resources\BinariesNET8\XNA\DTAConfig.pdb
+> ```
+
 4. **Apply the migration steps:**
    - If updating to next version: follow the instructions from release notes mentioned in step 1.
    - If updating skipping multiple versions, either: