Allow adding custom tokens to tunnel

[gndelia]

Feature or change description

Users should be able to tunnel tokens not listed on hemi.

See Design here

Proposed implementation

• Users will save the added token in their local storage
• Information of the token will be read from the L1/L2 chain, or added by the user if needed

[gndelia]

Reopening because there's a feature missing yet: The tooltip token and the ability to remove a custom added token (It's on figma, it wasn't implemented as part of #677 nor #687