[Feature]: Add a numeric keypad to call screen to dial DTMF

[DrDimedrol]

Precondition

• [X] I understood that this template is only for feature requests and not for bug reports

Cross-checked related issues?

• [X] I have cross-checked this overview https://github.com/monal-im/Monal/issues/322 as well as filtered for related labels https://github.com/monal-im/Monal/labels

Describe your feature

I'm a user of JMP.chat to make voice calls to telephone numbers and often need to call DTMF codes. Is it possible to have a numeric keypad in call screen? Monal version appstore 6.4.4

[lissine0]

This is already planned. See https://monal-im.org/post/00013-nlnet-funding2/