Add LF icon

[petervdonovan]

Recently VS Code was updated to allow extensions to contribute icons when the main icon theme (which is most commonly seti) does not provide them. We should take advantage of this feature.

[lhstrh]

Is this an icon for files or for something else? We already have an icon checked in here; what is that one used for?

[petervdonovan]

Files. That icon which we already have checked in appears when you look up our extension on the marketplace.

It is very easy to add our own file icon. The hard part is creating the icon.

[lhstrh]

Is there a spec for the icon format? Size and extension?

[petervdonovan]

Some information is provided here.

[petervdonovan]

When I tried using a PNG like what is currently in the images folder of this repo, I found that it did not look very good because the image was just a little bit too large/detailed. In order to close this issue we might need a slightly smaller icon. This is not something we should prioritize.