Fix - APP-2553 Refactor to use CSS animation in mobile menu

[jamesej]

Description

Fixing QA issue with original solution for APP-2553, this is a new PR for this ticket
Uses CSS animation and standard events to get same result as framer-motion lib and work with new modal system

Task: APP-2553

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran all tests with success and extended them if necessary.
• I have updated the CHANGELOG.md file in the root folder.
• I have tested my code on the test network.

[cgero-eth]

Thanks @jamesej, tested it and it works as expected now 👌🏻

[github-actions]

WebApp IPFS Hash: QmYSx4RzjDuQwkg8B9TPJ25RL4ENr9V86r2rfedwLvccU7
WebApp deployed to https://ipfs.eth.aragon.network/ipfs/QmYSx4RzjDuQwkg8B9TPJ25RL4ENr9V86r2rfedwLvccU7/