snapcraft.yaml: add dependency on remote indicator parts

[3v1n0]

This adds dependency on indicator- parts
to add support to desktop indicators with snap
support patches.

Parts are currently defined at:

• https://github.com/3v1n0/appindicators-snapcraft-parts

While examples of indicators for various toolkits are

• https://github.com/3v1n0/indicators-examples-snaps

[3v1n0]

Reproposing this after snapcraft with proper remote indicators has been released

[didrocks]

Looking good! However, we did merge now the GNOME desktop runtime as well. Do you mind looking at them if your PR doesn't need to change?
I think, for both Qt and GNOME desktop runtime, we don't want to have two depending part, but ensuring we have everything needed in the runtime and just embeeding everything in the platform snap, if that makes sense to you.

[3v1n0]

Sure, let me check that...

[3v1n0]

If we want to include indicator-gtk3 directly into the runtime, I guess this is fine to merge, isn't it?

[didrocks]

Correct, that's fine by me (as you didn't set after: in the platform ones, which should be part of the runtime (but maybe package-based)). Merging! 👍