Create 0.6 flatpak release

[bk138]

Get a beta v0.6 release out. Far from perfect, but fix most annoying papercuts and fullscreen toggle, tackled in #143 .

• [x] update wxglade
• [x] fix prefs window cutoff
• [x] fix stray entry in about->contributors -> fixed by using "translator-credits" in at least one .po file
• [x] enable all vnc auths
• [x] update all email addresses and copyright years
• [x] add link to issue list
• [x] decide about window sharing
• [x] decide about edge connector
• [x] test record/replay
• [x] write appstream data file
• [x] test seamless edge connector
• [x] email bug report
• [x] extend libvnc listen to rebind
• [x] set release dates and tag
• [x] PR at flathub : https://github.com/flathub/flathub/pull/4160

[bk138]

emailing of bug report

• https://github.com/wxWidgets/wxWidgets/blob/master/samples/debugrpt/debugrpt.cpp#L89 but this does not exist
• https://docs.wxwidgets.org/3.0/group__group__funcmacro__misc.html#ga3ff36fe489da2a779248b56f283615ca with mailto: might work
• https://stackoverflow.com/questions/154536/encode-decode-urls-in-c