Fix header formatting of Plugins.md
Fix header formatting of Plugins.md

NathanaelA/nativescript-cli,tsvetie/nativescript-cli,NathanaelA/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,tsvetie/nativescript-cli,tsvetie/nativescript-cli,tsvetie/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,tsvetie/nativescript-cli,NativeScript/nativescript-cli