doc: add requirement for two acks for changes
doc: add requirement for two acks for changes

- Two ACKs should be required to ensure that the maintainer guidelines
  remain credible.

A-Paul/RIOT,miri64/RIOT,BytesGalore/RIOT,yogo1212/RIOT,aeneby/RIOT,smlng/RIOT,x3ro/RIOT,jasonatran/RIOT,OTAkeys/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,toonst/RIOT,kaspar030/RIOT,avmelnikoff/RIOT,toonst/RIOT,authmillenon/RIOT,authmillenon/RIOT,OlegHahm/RIOT,rfuentess/RIOT,x3ro/RIOT,OlegHahm/RIOT,ant9000/RIOT,mtausig/RIOT,RIOT-OS/RIOT,lazytech-org/RIOT,ant9000/RIOT,cladmi/RIOT,mtausig/RIOT,x3ro/RIOT,BytesGalore/RIOT,biboc/RIOT,smlng/RIOT,RIOT-OS/RIOT,aeneby/RIOT,cladmi/RIOT,rfuentess/RIOT,biboc/RIOT,A-Paul/RIOT,basilfx/RIOT,aeneby/RIOT,basilfx/RIOT,authmillenon/RIOT,authmillenon/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,biboc/RIOT,cladmi/RIOT,yogo1212/RIOT,josephnoir/RIOT,jasonatran/RIOT,lazytech-org/RIOT,miri64/RIOT,josephnoir/RIOT,toonst/RIOT,authmillenon/RIOT,kbumsik/RIOT,cladmi/RIOT,kYc0o/RIOT,kbumsik/RIOT,BytesGalore/RIOT,josephnoir/RIOT,ant9000/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,smlng/RIOT,ant9000/RIOT,aeneby/RIOT,yogo1212/RIOT,lazytech-org/RIOT,mtausig/RIOT,jasonatran/RIOT,mtausig/RIOT,jasonatran/RIOT,gebart/RIOT,RIOT-OS/RIOT,avmelnikoff/RIOT,toonst/RIOT,toonst/RIOT,avmelnikoff/RIOT,basilfx/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,rfuentess/RIOT,gebart/RIOT,kbumsik/RIOT,A-Paul/RIOT,gebart/RIOT,kbumsik/RIOT,yogo1212/RIOT,lazytech-org/RIOT,rfuentess/RIOT,gebart/RIOT,biboc/RIOT,avmelnikoff/RIOT,yogo1212/RIOT,kbumsik/RIOT,smlng/RIOT,basilfx/RIOT,gebart/RIOT,mfrey/RIOT,kYc0o/RIOT,mfrey/RIOT,miri64/RIOT,biboc/RIOT,josephnoir/RIOT,aeneby/RIOT,miri64/RIOT,kaspar030/RIOT,basilfx/RIOT,cladmi/RIOT,mfrey/RIOT,A-Paul/RIOT,OTAkeys/RIOT,kYc0o/RIOT,josephnoir/RIOT,OlegHahm/RIOT,mtausig/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,x3ro/RIOT,kaspar030/RIOT,BytesGalore/RIOT,BytesGalore/RIOT,x3ro/RIOT,yogo1212/RIOT,kaspar030/RIOT,kaspar030/RIOT,authmillenon/RIOT,mfrey/RIOT,OTAkeys/RIOT,lazytech-org/RIOT,smlng/RIOT,mfrey/RIOT,kYc0o/RIOT,miri64/RIOT