• Added an entry to CHANGELOG.md if this change could be valuable to users

Adds the ability to view the expansion from completion as phantom text where the cursor is.
(VSCode has this feature as well, under the name 'Suggestion Preview'.)

(Might be nice to make snippets mark the places in the completion lens)

• This is disabled by default, since VSCode disables it by default. I could imagine enabling it by default, but since it is not typical it may be distracting for most users since they aren't used to it.
• The completion lens would appear in multiple editor views of the same document. I don't think this is really a problem, and making it only appear in the active document would require some modification of the code to have some per-editorview document textlayouts?
• Multiline completion items are cut off at the moment, because we don't have support for 'fake' lines in the document code