Add result to @batteries

[ffrostfall]

Many operations involving the file system & networking can fail. One of the most common ways of handling this is pcall, but this is not type safe.

A common idiom is to have a Result type, somewhat similar to Rust's Result type. It's an extremely common and useful idiom. Any project written in Lute interacting with APIs which could error will end up encountering the problem of gracefully handling failure; the result battery significantly helps with that.

[aatxe]

PR description?

[aatxe]

Do we want this over a form where err's type can be specified?

[ffrostfall]

Yes, kind of? The reason why is so that result failures can be appended. For example:

local function someOperation()
  return result(false, "failed to do generic operation")
end

local function meow()
  local call = someOperation()
  if not call then
    call.err = `failure in function "meow"; {call.err}`
  end
end

local function meow2()
  local call = someOperation()
  if not call then
    call.err = `failure in function "meow2"; {call.err}`
  end
end

err as string is great for propagating messages. Maybe we could attach something like errMessage and err to have both? I can see the value in, say, an error tagged enum.