Node Sass version 6.0.0 is incompatible with ^4.0.0.

This error message indicates that the version of Node Sass being used is not compatible with the range of versions specified in the package.json file. Specifically, the package.json file includes a range of versions starting with "^4.0.0" which indicates that any version of Node Sass starting with version 4 should be compatible. However, the current version being used is version 6.0.0 which is outside of this range.

To resolve this issue, you can either update the range of versions in the package.json file to include version 6 or install a version of Node Sass that falls within the specified range. You can install a compatible version of Node Sass by running the following command:

npm install node-sass@4.x

This will install the latest version of Node Sass that falls within the range specified in the package.json file.