Use QWebEngineView for Manual Panel
The TaurusMainWindow "Manual" Panel uses the deprecated QtWebkit.QWebView
widget for displaying the manual (see #1163 (closed)), which is not directly available from PyQt5 or PySide.
Replace it by its successor QtWebEngineWidgets.QWebEngineView
which can be imported in both PyQt5 and PySide2
Also, Add taurus.external.qt.QtWebEngine
and taurus.external.qt.QtWebEngineWidgets
Closes #1163 (closed)
Edited by Carlos Pascual