DS-751: Add support for placeholders to Bolt-only version of |t filter

[remydenton]

Jira

https://pegadigitalit.atlassian.net/browse/DS-751

Summary

Adds support for placeholders in translatable strings

Details

Proper string translation requires the ability to use variables. For example, if you wanted to translate the string "Tom's Profile", where "Tom" was a variable that corresponded to the user's name, you couldn't just expect a translator to convert "'s profile" into, say, Spanish.

Instead, you should ask the translator to translate "@user's profile". A Spanish translator could then understand the context of what they were translating and rearrange the words to "Perfil de @user".

This PR adds support for basic placeholders in translated strings in Bolt to match how the Drupal |t filter already works in Drupal. See https://www.drupal.org/docs/theming-drupal/twig-in-drupal/filters-modifying-variables-in-twig-templates#s-translation-filters for more details

How to test

To test, you could create a string that contains a placeholder variable and confirm that it's output correctly. An example is shown in 4c868ea, so you could confirm that it's working as expected on that PR.

[colbytcook]

Approved, confirmed that this method both on the Video Thumbnail twig and my own investigation