Fix #2336: CookieConsent cannot be hidden properly on very small screens

[lindapaiste]

Fixes #2336

Changes:

• The change in position is based on the height of the element rather than a fixed amount.
• bottom is always 0.
• The change now comes from a transform translateY.
• I used 105% instead of 100% because I was paranoid that the top 1px of the banner might sometimes be visible due to rounding errors if the banner starts exactly below where the screen ends. Not sure if this is an actual issue but I figured it's better to be safe. 🤷

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[PiyushChandra17]

Nicely Done

[raclim]

Thank you for working on this!