Add Twig switch/case extension

[codechefmarc]

Summary

Adds a new switch/case extension to Twig allowing for switch/case from within templates.

This PR fixes/implements the following bugs/features

• Adds a new Twig extension for switch/case statements
• Updates README.md with documentation on how to use this new feature

Explain the motivation for making this change. What existing problem does the pull request solve?

Continue adding new functionality to Emulsify Tools.

Documentation update (required)

Yes. README.md was updated with new information also copied here for eventual inclusion on the Emulsify website:

This adds the ability to do a switch/case function from within Twig templates. To use:

{% switch content.field_name.0 %}
    {% case "text" %}
      <p>This appears if the field name value is set to "text"</p>
    {% case "image" %}
      <p>This appears if the field name value is set to "image"</p>
    {% default %}
      <p>The field text did not match any case.</p>
{% endswitch %}

Note that the switch, endswitch, and case tags are required and the default is optional.

How to review this pull request

• Add the following to the composer.json repositories section:

{
  "type": "vcs",
  "url": "https://github.com/emulsify-ds/emulsify_tools.git"
}

• Go into your modules folder and delete any existing emulsify_tools that are already there
• From the root of the project, run composer require emulsify-ds/emulsify_tools --prefer-source
• Go into the directory where emulsify_tools now resides
• Change to this branch git checkout switch-case
• Make sure emulsify_tools is installed
• Go into a Twig template and write something like this:

{% set variable_name = "item 1" %}

{% switch variable_name %}
  {% case "item 1" %}
    Do something here only if the variable is set to "item 1"
  {% case "item 2" %}
    item 2 things
  {% default %}
    This is default if the variable doesn't match
{% endswitch %}

• Verify that the switch/case statement works as intended
• Change the variable to "item 2" and verify that the output is different
• Verify that by removing the optional default tag, that the function still runs as intended
• Test other uses cases such as: from within a for loop

[joetower]

@codechefmarc This is awesome, great work! Everything appears to work as you've outlined.