fix: organize imports to satisfy gci linter

- Add blank line between local and external imports
- Fixes CI linting failure

Author: d0ugal

cmd/main.go

@@ -10,7 +10,6 @@ import (
 	"ghcr-exporter/internal/config"
 	"ghcr-exporter/internal/metrics"
 	"ghcr-exporter/internal/version"
-
 	"github.com/d0ugal/promexporter/app"
 	"github.com/d0ugal/promexporter/logging"
 	promexporter_metrics "github.com/d0ugal/promexporter/metrics"