[core] include main-panel branding when empty

[vince-fugnitto]

• Added some branding to the main-panel when there are no editors or widgets
  present in the panel.

I thought Theia could use some branding options when there is no content in the main-panel, I am open however to programatically add the background image so that other products can more easily define their own branding. This is more of a proof of concept and I am open to changes/suggestions/ideas.

Dark	Bright

In the future we can also include common commands, helpful tips and links, the possibilities would be endless. For reference, here is vscode:

Signed-off-by: Vincent Fugnitto [email protected]

[vince-fugnitto]

Thanks @akosyakov, I hadn't thought of implementing it with css variables earlier.
I updated the PR, and also made the size a variable in case a product would like to change that as well!

[akosyakov]

logos should be part of distributed files of core package, i.e. belong to styles folder

otherwise it won't work outside of Theia repo

[vince-fugnitto]

logos should be part of distributed files of core package, i.e. belong to styles folder

otherwise it won't work outside of Theia repo

thanks for clarifying, I updated the PR based on your comment. I placed it under the icons folder, if it should be under a different or new folder just let me know.

[svenefftinge]

We should move this to a 'branding' extension where we show how to provide product branding information by doing so by example for Theia.
The 'getting-started' extension could possibly be renamed to 'theia-branding' and contain more information (like logos, etc.).
Core could provide a contribution where a branding extension can hook in and provide the needed information.

[svenefftinge]

Stuff like #3600 should be done like that as well.

[svenefftinge]

And this one #3886

[vince-fugnitto]

@svenefftinge @akosyakov
should I keep this PR on hold in favour of adding a branding extension this month that contributes the branding, logos, etc. and make the adjustments to core to accept a contribution hook?

[akosyakov]

@svenefftinge what do you mean by hooks? would properties in package.json work? We already have a section to provide configurations: https://github.com/theia-ide/theia/blob/b00646483ce663746ac8515cb945e680a9df2af2/examples/browser/package.json#L5-L11