setting `linters.markdownlint-cli.cmd` would genenrate
before:
`linters.markdownlint-cli.cmd` resulting in an error.
after:
`linters["markdownlint-cli"]["cmd"]`
Those types needed the following code in apply:
if builtins.isString value
then mkRaw value
else value
This commit avoids this boilerplate, and clarifies that the `str` is lua
code in the documentation.