[#2142] Fix Vulnerabilities

[sopa301]

Fixes #2142

Proposed commit message

Fix Vulnerabilities in Code Base

There are existing vulnerabilities in the code base.

Let's fix as many as possible.

Other information

@vue/cli-service is being put on maintenance mode. It might be worthwhile to migrate to the suggested create-vue to keep dependencies updated.

postcss and vue-loader had to be installed manually because @vue/cli-service is not updated with the fixed dependencies yet. These can be removed when @vue/cli-service has a similar update.