tests: pkg_u8g2: improve readme.
tests: pkg_u8g2: improve readme.

yogo1212/RIOT,adrianghc/RIOT,TobiasFredersdorf/RIOT,hamilton-mote/RIOT-OS,ant9000/RIOT,TobiasFredersdorf/RIOT,cladmi/RIOT,beurdouche/RIOT,cladmi/RIOT,Josar/RIOT,kaspar030/RIOT,immesys/RiSyn,kaspar030/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,jasonatran/RIOT,x3ro/RIOT,basilfx/RIOT,avmelnikoff/RIOT,ks156/RIOT,wentaoshang/RIOT,kerneltask/RIOT,kerneltask/RIOT,beurdouche/RIOT,d00616/RIOT,OlegHahm/RIOT,mfrey/RIOT,tfar/RIOT,dkm/RIOT,kYc0o/RIOT,kYc0o/RIOT,roberthartung/RIOT,lazytech-org/RIOT,Josar/RIOT,Hyungsin/RIOT-OS,mtausig/RIOT,LudwigKnuepfer/RIOT,dkm/RIOT,aeneby/RIOT,thomaseichinger/RIOT,jbeyerstedt/RIOT-OTA-update,rajma996/RIOT,rfuentess/RIOT,Hyungsin/RIOT-OS,wentaoshang/RIOT,toonst/RIOT,katezilla/RIOT,yogo1212/RIOT,jremmert-phytec-iot/RIOT,jbeyerstedt/RIOT-OTA-update,dailab/RIOT,kbumsik/RIOT,adjih/RIOT,biboc/RIOT,adrianghc/RIOT,neumodisch/RIOT,kb2ma/RIOT,authmillenon/RIOT,kaleb-himes/RIOT,rajma996/RIOT,backenklee/RIOT,BytesGalore/RIOT,mtausig/RIOT,jasonatran/RIOT,x3ro/RIOT,dkm/RIOT,dkm/RIOT,adrianghc/RIOT,LudwigKnuepfer/RIOT,yogo1212/RIOT,biboc/RIOT,syin2/RIOT,RIOT-OS/RIOT,gebart/RIOT,toonst/RIOT,wentaoshang/RIOT,LudwigOrtmann/RIOT,tfar/RIOT,jremmert-phytec-iot/RIOT,jbeyerstedt/RIOT-OTA-update,d00616/RIOT,jfischer-phytec-iot/RIOT,RIOT-OS/RIOT,neumodisch/RIOT,kerneltask/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,kaspar030/RIOT,dailab/RIOT,basilfx/RIOT,BytesGalore/RIOT,thomaseichinger/RIOT,thomaseichinger/RIOT,lazytech-org/RIOT,neiljay/RIOT,altairpearl/RIOT,toonst/RIOT,d00616/RIOT,mtausig/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,neumodisch/RIOT,kaleb-himes/RIOT,LudwigKnuepfer/RIOT,smlng/RIOT,altairpearl/RIOT,OTAkeys/RIOT,Ell-i/RIOT,x3ro/RIOT,Hyungsin/RIOT-OS,josephnoir/RIOT,miri64/RIOT,gebart/RIOT,miri64/RIOT,tfar/RIOT,OTAkeys/RIOT,avmelnikoff/RIOT,ant9000/RIOT,A-Paul/RIOT,jfischer-phytec-iot/RIOT,x3ro/RIOT,plushvoxel/RIOT,neiljay/RIOT,cladmi/RIOT,ant9000/RIOT,miri64/RIOT,jasonatran/RIOT,hamilton-mote/RIOT-OS,alignan/RIOT,rfuentess/RIOT,gebart/RIOT,yogo1212/RIOT,kaspar030/RIOT,alignan/RIOT,ks156/RIOT,katezilla/RIOT,kaleb-himes/RIOT,smlng/RIOT,adjih/RIOT,rfuentess/RIOT,jfischer-phytec-iot/RIOT,TobiasFredersdorf/RIOT,LudwigKnuepfer/RIOT,ks156/RIOT,beurdouche/RIOT,LudwigOrtmann/RIOT,mfrey/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,roberthartung/RIOT,josephnoir/RIOT,gautric/RIOT,roberthartung/RIOT,immesys/RiSyn,altairpearl/RIOT,immesys/RiSyn,alignan/RIOT,miri64/RIOT,jremmert-phytec-iot/RIOT,biboc/RIOT,A-Paul/RIOT,altairpearl/RIOT,altairpearl/RIOT,yogo1212/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,neumodisch/RIOT,tfar/RIOT,Josar/RIOT,avmelnikoff/RIOT,ant9000/RIOT,BytesGalore/RIOT,hamilton-mote/RIOT-OS,plushvoxel/RIOT,altairpearl/RIOT,beurdouche/RIOT,gautric/RIOT,kbumsik/RIOT,alignan/RIOT,jremmert-phytec-iot/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,plushvoxel/RIOT,backenklee/RIOT,neumodisch/RIOT,cladmi/RIOT,adrianghc/RIOT,kbumsik/RIOT,Ell-i/RIOT,wentaoshang/RIOT,d00616/RIOT,BytesGalore/RIOT,roberthartung/RIOT,dailab/RIOT,kaleb-himes/RIOT,kb2ma/RIOT,avmelnikoff/RIOT,Ell-i/RIOT,tfar/RIOT,kb2ma/RIOT,mtausig/RIOT,kYc0o/RIOT,kb2ma/RIOT,Josar/RIOT,neumodisch/RIOT,ks156/RIOT,neiljay/RIOT,aeneby/RIOT,LudwigOrtmann/RIOT,thomaseichinger/RIOT,authmillenon/RIOT,kaspar030/RIOT,OTAkeys/RIOT,Ell-i/RIOT,lazytech-org/RIOT,TobiasFredersdorf/RIOT,LudwigOrtmann/RIOT,aeneby/RIOT,smlng/RIOT,katezilla/RIOT,kerneltask/RIOT,neiljay/RIOT,hamilton-mote/RIOT-OS,cladmi/RIOT,OlegHahm/RIOT,syin2/RIOT,katezilla/RIOT,A-Paul/RIOT,ks156/RIOT,d00616/RIOT,smlng/RIOT,gautric/RIOT,kerneltask/RIOT,josephnoir/RIOT,mtausig/RIOT,plushvoxel/RIOT,kbumsik/RIOT,basilfx/RIOT,avmelnikoff/RIOT,BytesGalore/RIOT,gautric/RIOT,wentaoshang/RIOT,jfischer-phytec-iot/RIOT,LudwigKnuepfer/RIOT,adjih/RIOT,jremmert-phytec-iot/RIOT,syin2/RIOT,yogo1212/RIOT,rajma996/RIOT,OlegHahm/RIOT,neiljay/RIOT,immesys/RiSyn,OTAkeys/RIOT,toonst/RIOT,katezilla/RIOT,dkm/RIOT,wentaoshang/RIOT,biboc/RIOT,basilfx/RIOT,adjih/RIOT,rajma996/RIOT,Josar/RIOT,aeneby/RIOT,beurdouche/RIOT,A-Paul/RIOT,rfuentess/RIOT,roberthartung/RIOT,rajma996/RIOT,d00616/RIOT,adrianghc/RIOT,kbumsik/RIOT,authmillenon/RIOT,adjih/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,backenklee/RIOT,authmillenon/RIOT,basilfx/RIOT,mfrey/RIOT,authmillenon/RIOT,immesys/RiSyn,immesys/RiSyn,gebart/RIOT,mfrey/RIOT,gebart/RIOT,thomaseichinger/RIOT,josephnoir/RIOT,A-Paul/RIOT,jbeyerstedt/RIOT-OTA-update,LudwigOrtmann/RIOT,miri64/RIOT,hamilton-mote/RIOT-OS,alignan/RIOT,authmillenon/RIOT,biboc/RIOT,backenklee/RIOT,kaleb-himes/RIOT,syin2/RIOT,aeneby/RIOT,jbeyerstedt/RIOT-OTA-update,Hyungsin/RIOT-OS,backenklee/RIOT,josephnoir/RIOT,jfischer-phytec-iot/RIOT,dailab/RIOT,kb2ma/RIOT,LudwigOrtmann/RIOT,syin2/RIOT,kYc0o/RIOT,jasonatran/RIOT,jremmert-phytec-iot/RIOT,Hyungsin/RIOT-OS,TobiasFredersdorf/RIOT,x3ro/RIOT,smlng/RIOT,Ell-i/RIOT,RIOT-OS/RIOT,mfrey/RIOT,OTAkeys/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,kYc0o/RIOT,rajma996/RIOT,toonst/RIOT,plushvoxel/RIOT,ant9000/RIOT,gautric/RIOT,dailab/RIOT