Add support for snapcraft compression top-level key

Snap packages are known for having a very long first startup time. That’s mainly because snaps are compressed squashfs images using XZ algorithm. Recently Canonical made it possible to use LZO algorithm instead of XZ, which significantly improves startup time.

I’d like to ask for electron-builder to support the snapcraft top-level key compression. From https://snapcraft.io/docs/snapcraft-top-level-metadata:

Sets the compression type for the snap. Can be xz or lzo. Defaults to xz when not specified. Snaps are compressed using xz data compression by default. This offers the optimal performance to compression ratio for the majority of snaps. However, there are certain types of snap, such as large desktop applications, that can benefit from using LZO compression. Snaps compressed with lzo are slightly larger but can decompress quicker, reducing the time it takes for freshly installed or refreshed snaps to launch.

More info:

• https://forum.snapcraft.io/t/how-to-switch-your-snap-to-use-lzo-compression/21714
• https://snapcraft.io/blog/snap-speed-improvements-with-new-compression-algorithm

This is related to bitwarden/clients#2609

[ppd]

I think the PR is almost complete. @mmaietta maybe you can have a quick look over the proposed changes sometime soon. It would be great to land this in the near future.

[om26er]

@pachulo @mmaietta I will take a dig at that during the weekend, will try to propose a fix then