Clarify download links wording to address MidnightCommander/mc#4703

Author: zyv

docs/index.md

@@ -43,7 +43,7 @@ The easiest way to install `mc` is to use your system package manager:
     % brew install midnight-commander
     ```
 
-Our source releases are kindly [mirrored by OSU OSL]({{ extra.downloads_url }}). Our canonical repository is hosted [on GitHub]({{ config.repo_url }}). See the [Source code](source-code.md) page for details.
+Download our source releases from the [official mirror]({{ extra.downloads_url }}) (thanks, OSU OSL!). Our [canonical repository]({{ config.repo_url }}) is hosted on GitHub. See the [Source code](source-code.md) page for details.
 
 ## Documentation