fix: ensure all created autocmds are part of the Neogit augroup

[PriceHiller]

Prior to this PR using vim.api.nvim_get_autocmds({ group = "Neogit" }) would only return the initial setup autocmds that Neogit created. It did not return the autocmds created for the buffers that Neogit created.

This PR enables users to get all the autocmds that Neogit creates. It does this by exporting the augroup in autocmds.lua and then importing it in buffer.lua so they share the same augroup.

Something to note, we may want to create a different augroup for the Neogit buffers in buffer.lua instead of using the same augroup in autocmds.lua, though it may make it a bit more difficult to search for.

[CKolkey]

The only thing I'd say is to move the group into the setup, since I kinda have short-term plans to remove that autocmds file. You can check that out here CKolkey#44 if you're curious. Otherwise this makes perfect sense :)

[PriceHiller]

Do you mean within the setup function in autocmds.lua or elsewhere? Like the setup function in the primary file?

The only other convenient place I see to set the augroup is in the config table.

[CKolkey]

Sorry, I mean the setup function for the plugin: https://github.com/NeogitOrg/neogit/blob/master/lua/neogit.lua

Then export it from the module, and consume it where needed. Or something like that.

[PriceHiller]

@CKolkey done. Take a look and let me know what you think.

[CKolkey]

I think it looks great :D