[TRA-1694] Improve Performance Score

[filipechagas]

TRA-1694

Description

Latest changes improved CLS but dropped LCP. This PR is an attempt of fixing it. This change will also improve best practices score by removing a javascript library dependency with known security issues: Upgrade jquery from 3.4.1 to 3.6.0 (the latest version by the time of this PR)

Related to https://github.com/toptal/gitignore.io/pull/534

How to test

• docker-compose -f ./docker-compose-dev.yml build
• docker-compose -f ./docker-compose-dev.yml up
• go to http://localhost:8080
• verify that the app is still overall working
• verify e2e tests are passing with yarn test
• use browser performance tools with webvitals enabled to check for issues