Decision chart in Readme.md cannot be viewed in dark mode

[mjperez-usgs]

I am running Windows 11 and have set my system theme to dark theme. This causes Github to also be in dark theme, which makes the decision chart in the Readme.md file unable to be viewed.

The decision tree lines should have a white stroke (or the opposite), or be in grey, so it is visible in both.

[mjperez-usgs]

It appears in the wiki, there is a version that has a white background, which should be copied to the readme: https://github.com/digital-analytics-program/gov-wide-code/wiki