Remove vendor folder

Problem/Motivation

The vendor folder has been committed to the repository. This is not a best practice and should be avoided.

Steps to reproduce

See /vendor

Proposed resolution

Add any dependency which is not yet in the composer.json file and remove the vendor folder as a whole.
Add a .gitignore to prevent accidental re-adding

Remaining tasks

MR

User interface changes

N/A

API changes

N/A

Data model changes

N/A