feat: add support for snap packages

[gapplef]

The snapcraft.yaml is quite straightforward. I'll explain a little bit, in case you may want to change it in the future.

On the top is various meta information, only things to be care are grade and confinement:

• grade can be devel or stable, defines the quality grade of the snap.
• confinement can be strict or classic, the latter means the snap have full system access just like traditionally applications.

The packing process is defined in parts section.

• Building is take care by rust plugin, and carry out with craftctl default. You may replace it with any custom build commands.
• craftctl set version=... is used to set the version info.
• The rest is all for dependencies.
  current only fd-find, ripgrep, zoxide, fzf are boundle with yazi, these may need to be change with requirements.

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As for the release workflow, I did not add new matrix, current build is take place on x86_64-unknown-linux-gnu with snapcore/action-build@v1. The release file would be yazi*.snap.
The snap package can be install with sudo snap install <package.snap> --dangerous --classic

Finally, to make it easier for users to get future updates, the snap can be publish to snap store. Snapcraft also provide its own build service to automatic build and release snaps.

[sxyazi]

Thank you for your work and detailed description, let me make some minor changes and then merge it!