Show entries immediately in menu after configuring

[MorrisJobke]

• currently you need to reload the page when configure a menu entry
• it should be the same as with enabling apps: after setting it up it should be added to the menu
• from Nextcloud 12 overview server#2672

[nickvergessen]

See #11 and #19

Only doesn't work for the settings menu atm, caused by reasons out of scope of this app.