Allow disable style overwriting

[cilerler]

While the themes are useful, they limit seeing the original code.
It would be great to have a way to disable it and show exactly what the colors are set in the code as is.

actual

expected

code to reproduce

@startmindmap Tools

*[#000000] <color:#FFFFFF><&infinity> ChromeBook

** Collaboration
***_ <b>Gmail Workspace</b> \n<i>(Voice, Chat, \n<i>Meet, \n<i>Email, Calendar, Tasks, Keep, \n<i>Drive, Docs, Sheets, Slides, Forms, Drawing, Sites, \n<i>Tables, DataStudio)

** Phone
***_ Google Voice
***_ <strike><color:#B71C1C>Zoom</strike>

** Chat
***_ Google Chat
***_ <strike><color:#B71C1C>Microsoft Teams</strike>
***_ <strike><color:#B71C1C>Slack</strike>

** Remote support
***_ Google Remote Desktop
***_ Microsoft Remote Desktop
***_ <strike><color:#B71C1C>TeamViewer</strike>

** Cloud
***[#1B5E20] <color:#E8F5E9>Google Cloud
***[#0D47A1] <color:#E3F2FD>Microsoft Azure

** Screen-Capture
***[#F44336] <color:#FFEBEE>TechSmith Snag-it

** Async meeting
***[#F44336] <color:#FFEBEE>TechSmith Snag-it
***[#FDD835] <color:#212121>Loom

** eSign and Document archiving
***_ Adobe PDF Pro

** Ticketing
***_ Zendesk
***_ Kayako

@endmindmap