Force single app instance on windows
Force single app instance on windows

fixes issue #236

St-Ex/desktop,mattermost/desktop,yuya-oc/electron-mattermost,jnugh/desktop,yuya-oc/desktop,St-Ex/desktop,yuya-oc/desktop,yuya-oc/electron-mattermost,mattermost/desktop,mattermost/desktop,yuya-oc/electron-mattermost,mattermost/desktop,yuya-oc/desktop,St-Ex/desktop,jnugh/desktop,jnugh/desktop,mattermost/desktop