Feature: Add *selection* placeholder for inserting HTML snippets (fragments)

[RealRaven2000]

Improvement for the new insert Snippets feature from issue #142 - if the text *selection* is added, take any selected text and replace it into the snippet instead.

Example:

<style>
  code.html { 
    font-family: Consolas, 'Courier New', Geneva, sans-serif !important;
    color: #303030;
    border: 1px solid #bbb;
  }
</style>
<code class="html">&lt;*selection*&gt;</code>

If you have an email with the word "div", highlight the text "div" and then load the template above. This should replace the "div" with the HTML code below, and style it with a monospaced font:

<code class="html">&lt;div&gt;</code>

Note: I usually put my css rules in separate css files which I import with the %style()% command as part of my general support templates.

[RealRaven2000]

Implemented in 3.9 - released on 09/12/2021