README: clarify solder instruction regarding vertical pin header related to https://github.com/kinx-project/kint/issues/13

reference kint36 pull request

README: which teensy: add consideration regarding advanced QMK feats

README: link adapter board

kint2pp: link to QMK commit

kint2pp: reference QMK pull request

update README for release

update artifacts for v2020-06-30

adjust silkscreen, route traces to enable GND plane filling

teensy: update silk screen to indicate sizes and compat