Problem:
`any[]` means nothing, and the return value is not the same as what's
documented in the comment (eg, Lua returns `{ "row", { { "leaf", 1000 },
{ "leaf", 1001 } } }`, not `{ "row", { "leaf", 1000, "leaf", 1001 } }`)
Solution:
Create two classes (vim.fn.winlayout.leaf and vim.fn.winlayout.branch)
and one alias that links the two together.
Also: Due to LuaLS limitations, there is an empty class,
vim.fn.winlayout.empty
Signed-Off-By: VoxelPrismatic <voxelprismatic@pm.me>