feat: introduce condensed theme

[boxdot]

Closes #414

[victormihalache]

The only issue I see is the read receipts not being settable.

IMO handling read receipts should be done as such:

• If default theme: show them
• If condensed theme: hide them
• If condensed theme, but read receipts explicily set: show them.

[victormihalache]

also, i personally don't agree with the date not being shown in compact mode... maybe instead of a "theme" there should be "bits" you can just toggle(?)