add 0.20.2 release notes [skip ci]

add 0.20.1 release notes [skip ci]

update screenshot for 0.20.0 [skip ci]

add 0.19.9 release notes [skip ci]

add 0.19.8 release notes [skip ci]

add 0.19.7 release notes [skip ci]

add 0.19.6 release notes [skip ci]

add 0.19.5 release notes [skip ci]

fix duplicate provides tag in appdata.xml

add 0.19.3 release notes [skip ci]