Introduce support to `textEdit` completion items

[karreiro]

Introduce support for textEdit Completion Items for Liquid tags.

A CompletionItem incorporates support for the textEdit field.

The objective of this task is to assess (and implement if feasible) the possibility of using textEdit to enhance code completion for Liquid tags. For instance, the language server could provide code completion for a for tag and automatically close it.

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⚠️ Notice: An essential aspect of this task is to evaluate the impact on the Shopify/code-mirror-language-client, which might need to integrate support for textEdit as well.

[charlespwd]

I feel like we do that with tag snippets now. Might be other places where we could add this.