MIR-1333 Added placeholder for username input field in new-author.xed#1037

Possommi wants to merge 2 commits into2023.06.xMyCoRe-Org/mir:2023.06.xfrom

issues/MIR-1333-new-author.xed-should-contain-hints-which-characters-are-allowed-for-a-usernameMyCoRe-Org/mir:issues/MIR-1333-new-author.xed-should-contain-hints-which-characters-are-allowed-for-a-usernameCopy head branch name to clipboard