Update build command to output executable for Windows

Author: Sentinel-Gate

README.md

@@ -81,7 +81,7 @@ sudo mv sentinel-gate /usr/local/bin/
 
 ```bash
 git clone https://github.com/Sentinel-Gate/Sentinelgate.git
-cd Sentinelgate && go build -o sentinel-gate ./cmd/sentinel-gate
+cd Sentinelgate && go build -o sentinel-gate.exe ./cmd/sentinel-gate
 ```
 
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