Added endo.link to Allowed Hosts

This will be necessary for the site to be hosted.

Description

Please include a summary of the change and which issue is resolved. List any dependencies that are required for this change.

Enables http://endo.link to host the webserver.

Please delete options that are not relevant.

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

Please check [x] all that apply.

[x] My code follows similar styling to existing code in this project
[x] I have performed a self-review of my own code
[ ] I have commented my code, at the very least in hard-to-understand areas
[ ] I have made corresponding changes to documentation / READMEs
[x] My changes generate no new warnings
[x] I have remade my frontend and backend Docker containers to ensure my changes do not break the setup for these
[ ] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[x] I have checked my code and corrected any misspellings