Allow switch statements in TemplateMark

[OliverTod]

This issue extends #588.

Requested functionality:
Extend TemplateMark so that more complex conditional statements can be used in a bidirectional way. That is, so that users can draft and parse with greater flexibility. This could be done by allowing switch statements.

Switch statements
For example, in JavaScript a switch statement is written as:

switch(colourVariable){
  case "yellow":
  ...
  break

  case "red":
  ...
  break

  case "blue":
  ...
  break

  default:
  ...
  break
}

Maybe this could be written as: {{#switch colourVariable}}{{#case yellow}} ... {{#case red}} ... {{#case blue }} ... {{#default}} ... {{/switch}}

[Bl4ck-h00d]

Hi! I would like to work on this feature. Can you please guide me how to get started?

[aryanshukla7]

Hello, I would like to work on this, can you please guide me on how to get started!

[arpitmaurya]

@OliverTod @DianaLease Hello, I would like to work on this, can you please assigned me this issues