update CoC to 0.4

see https://github.com/Bantik/contributor_covenant
update CotEditor to 1.5.4
Merge pull request #5138 from vitorgalvao/fix-5137

update CotEditor to 1.5.4
Connector 2.2.3
Add Placeit version 1.7.2

Place Your App in a Stage! https://placeit.net
Merge pull request #5136 from leoj3n/connector-2.3.3

Connector 2.3.3
updated imitone (0.5.3)
Merge pull request #5139 from vinkla/placeit

Add Placeit version 1.7.2
Merge pull request #5140 from vitorgalvao/imitone

updated imitone (0.5.3)
Merge pull request #4055 from caskroom/code-of-conduct-v0.4

update CoC to 0.4
Upgrade Thunder.app to v2.6.4.1616
Merge pull request #5142 from tolbkni/thunder

Upgrade Thunder.app to v2.6.4.1616