Distribute without a go compiler

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One of the reasons to chose golang as a remote plugin is that it can produce static binaries that can be easily distributed without a runtime or dependencies.

Currently darkman.nvim requires a go compiler to be installed, so that bin/darkman.nvim can be compiled on-site.
Ideally, we should release "packaged" versions with a binary included, so that a go compiler is not necessary to install the plugin.

[4e554c4c]

I created wbthomason/packer.nvim#1210 to discuss the possibility of downloading from a github release in packer

[4e554c4c]

lazy.nvim is also unfriendly to this idea: folke/lazy.nvim#780

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If something like packspec is used widely, we could switch to this: https://github.com/neovim/packspec