Add validation to link

[lissomliksom]

Describe the bug

The "Insert Link"-option has two errors or possibly unintended behaviours:

1. Inserting a link without text results in nothing showing. No link is inserted into the textarea. URL is required, but not Text. Consider adding required-property to text.
2. Inserting a link without "https://" and only "www" results in broken links. Consider automatically adding "https://" if only "www" is present, or throw validation error on insert/save.

Steps to reproduce

First issue: No link insertion

1. Click link icon
2. Select Insert Link
3. Add url, but no text
4. Click insert-button

Second issue: www

1. Click link icon
2. Select Insert Link
3. Add url starting with www
4. Click insert-button.
5. Preview entry and click link.

Craft CMS version

4.5.1

Plugin version

2.1.8

Multi-site?

No

Additional context

No response