Fix exec plugins on windows

The exec plugin implementation checks if an executable file exists but
on windows it won't check for files with .exe suffix thus falling back
to go plugin implementation

api/internal/plugins/loader/loader.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"plugin"
 	"reflect"
+	"runtime"
 	"strings"
 
 	"github.com/pkg/errors"
@@ -177,7 +178,11 @@ func (l *Loader) loadPlugin(res *resource.Resource) (resmap.Configurable, error)
 
 func (l *Loader) loadExecOrGoPlugin(resId resid.ResId) (resmap.Configurable, error) {
 	// First try to load the plugin as an executable.
-	p := execplugin.NewExecPlugin(l.absolutePluginPath(resId))
+	pluginPath := l.absolutePluginPath(resId)
+	if runtime.GOOS == "windows" {
+		pluginPath = fmt.Sprintf("%s.exe", pluginPath)
+	}
+	p := execplugin.NewExecPlugin(pluginPath)
 	err := p.ErrIfNotExecutable()
 	if err == nil {
 		return p, nil