reformat dotted keys as inline tables

[benluelo]

in Cargo.toml files, a common pattern to see is dep.workspace = true. this is quite noisy as it pollutes the lhs of the assignment, so i typically prefer dep = { workspace = true } (which also has the nice benefit of working nicely with align_entries). an option to convert a.b = c to a = { b = c } would be great!