feature: style vim.diagnostic.open_float

[drowning-cat]

Did you check the docs?

• I have read all the noice.nvim docs

Is your feature request related to a problem? Please describe.

vim.diagnostic.open_float looks a bit off comparing to vim.lsp.buf.hover.

vim.diagnostic.open_float	vim.lsp.buf.hover

Describe the solution you'd like

Add padding to vim.diagnostic.open_float to match the style of vim.lsp.buf.hover.

Describe alternatives you've considered

N/A

Additional context

N/A