Add qthttpserver module to qt5

Please add qthttpserver module to the qt5 hierarchy as a submodule. The submodule is to have status preview. Currently the repo is located here: https://codereview.qt-project.org/gitweb?p=qt-extensions/qthttpserver.git;a=summary. Only the dev branch needs to be imported. The outstanding merge requests to dev branch need to be migrated, if possible. There is no need to keep submodule update working for the qt-extensions repo after the new repo is created.

This is to advance work on QTBUG-100994. Earlier I wrote an email about this here: https://lists.qt-project.org/pipermail/development/2022-April/042343.html

CC: jefernan