Fixes calls deprecated in nvim 0.11.0.

Going through warnings LSP was giving meant revisiting the custom code
which applies goimports behavior on writes for Go files. I don't love
manually requesting a code action from the server, but I tried to do it
programmatically:

vim.lsp.buf.code_action({
context = {
diagnostics = {},
only = { "source.organizeImports" },
triggerKind = vim.lsp.protocol.CodeActionTriggerKind.Automatic,
},
apply = true,
})

... and this had a couple of problems:

1. writes which didn't need to do imports would always print the message
"no code actions available" and I couldn't see anything in the API to
make this quiet
2. the code action would happen asynchronously, so the write would
happen, then the imports would be fixed, and then another write would
still need to happen

Working around this might involve:

* being better at nvim APIs
* blocking in the function that calls code_action (like request_sync)
* only calling code_action if I know there are imports that need to be
done, maybe by checking diagnostics (to avoid the message being
printed)

See: https://neovim.io/doc/user/deprecated.html#deprecated-0.11

* add bprev mapping consistent with n/p convention
* add alias for git-aware ls, and explicitly gitignore .jj for eza's
sake
* add qemu disk files to gitignore

Bindings are mostly default except for navigation between splits.