Resolve issues with publishing

[dmytro-kashcheiev]

• Make sure the folder for credentials exists.
• Add changelog.
• Increase duration between command and query as far as it can unexpectedly fail.
• Update version in pubspec as well.
• Migrate publishing of the GH pages from the Travis to GH Actions.

[dmytro-kashcheiev]

@ptal again I've added GH pages publishing.

[armiol]

@dmytro-kashcheiev LGTM. However, I would also add the note on Travis -> GH Actions to the PR description.