[FEATURE] Allow editing merge tag attributes in the editor

[picocodes]

Description

Most merge tags accept attributes such as format and default values. Provide a way to display this in the email editor.

Describe the solution you'd like

Most merge tags that are shown as blocks allow editing this merge tags. For other tags we can add something such as a merge editor popup that displays the available fields.

Screenshots

No response

Additional information

No response

[scrobbleme]

Maybe switch to "Block Bindings" for merge tags (where possible)?
This would allow using the default styling options.

As of now, you have to insert Block Bindings manually (i.e. the enhanced paragraph block), but as you are already familiar with extending Gutenberg, you maybe could add some function for this.

Block Bindings itself are easy to implement and use.

Example:

<!-- wp:paragraph {
"metadata":{
    "name":  "Noptin: Name",
    "bindings":{"content":{
        "source":"noption/merge_tag",
        "args":{
            "key":"name"
            }
        }}}, 
"className":"text-decoration-none","fontSize":"small"} -->
<p class="text-decoration-none has-small-font-size">Noptin: Name</p>
<!-- /wp:paragraph -->