feat(icon): add internal folder icon

[SayanShankhari]

Resolves: #3328

Description

Add internal folder icons.
Thanks to @JonasLillebo for raising the issue.
Thanks @PKief @LilleboHaugen for going through the concepts.

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[SayanShankhari]

@LilleboHaugen, the sky-blue seems too light to me, can you choose some darker shade?

[PKief]

I'd also prefer a different color. I feel that light blue doesn't match the purpose of an internal folder

[LilleboHaugen]

Yes, no worries. I'm not good with colors, so go with whatever color you see fit 👍

[PKief]

I've made a mistake while resolving the conflicts, @SayanShankhari can you please remove the duplicated { name: 'folder-kotlin', folderNames: ['kotlin'] }, line? Thanks :)

[PKief]

Github is little hanging today on my end...