Inject Environment Variable for Github Pages Deployments in Vite Build

[sopa301]

Part of reposense/RepoSense#2257

Proposed commit message

Inject Environment Variable for Github Pages Deployments in Vite Build

Under the Vite build for Github Pages Deployments, the base directory
of the deployment needs to be specified in a configuration file during
build time. We can make this dynamic since the base directory is the
name of the deployment repository.

Let's modify the code to add the VITE_BASE_DIR environment variable for
Github Pages Deployments.

Other information

Note that this only works for the Github Pages and Travis (which uses Github Pages) methods specified in the RepoSense User Guide. It is unclear if the Netlify method works due to a separate issue.