setting boolean variables from lua only work with 1/0 not true/false

[lukas-reineke]

When setting boolean variables from lua, they are not converted to 1/0.
But the code only checks for == 1 etc

This doesn't work

vim.g.diagnostic_enable_virtual_text = true

This works

vim.g.diagnostic_enable_virtual_text = 1

I can make a PR to fix it, but not sure what the proper way to handle this is.
Have a util function that checks both 1/0 and true/false?