vue-demi@0.13.11 requires a peer of vue@^3.0.0-0 || ^2.6.0 but none is installed. You must install peer dependencies yourself.

This error message is indicating that the package "vue-demi" version 0.13.11 requires either version 3.0.0-0 or later or version 2.6.0 of the "vue" package as a peer dependency. However, it appears that neither of these versions of "vue" is currently installed in your project.

To resolve this error, you will need to install the required version of "vue" as a peer dependency. You can do this by running the following command in your project directory:

npm install vue@^3.0.0-0 || ^2.6.0 --save-dev

This will install the required version of "vue" as a development dependency in your project. Once the installation is complete, you should be able to use the "vue-demi" package without any further errors.