Add support for `case` and `when` tags

[charlespwd]

In this PR

• Add support for case tag
• Add support for when tag

Decisions

• Never break case
• Only break when when the undocumented comma or or syntax is used
  • Same way as the others

Examples

It should break and indent when statements, and not break the when
printWidth: 1
{% case candy.type %}
  {% when 'gummy bears' %}
    yum!
  {% else %}
    ok!
{% endcase %}

It should break on when comma syntax
printWidth: 1
{% case candy.type %}
  {% when 'gummy bears',
    'chocolate'
  %}
    yum!
  {% else %}
    ok!
{% endcase %}

It should break on when or syntax (and prefer commas)
printWidth: 1
{% case candy.type %}
  {% when 'gummy bears',
    'chocolate',
    'chips'
  %}
    yum!
  {% else %}
    ok!
{% endcase %}