Validate configuration against schema

[gegoune]

Is your feature request related to a problem? Please describe.
Keys of a table passed into setup() function are plenty, nested and can be very easily misplaced by users. There were issues reported in the past which were simply result of wrong nesting.

Describe the solution you'd like
It would greatly help if plugin was validating table against schema ensuring passed in configuration is valid.

Describe alternatives you've considered
Do nothing.

Additional context
Edit: this is how b0o achieved it in incline https://github.com/b0o/incline.nvim/blob/main/lua/incline/config/schema.lua.

[alex-courtis]

That would be very useful.

nvim-tree has a more complex configuration than incline, however it could cover the tables with entries e.g. view.mappings actions.open_file etc.

[alex-courtis]

Here's a case that this would have prevented #1157

[alex-courtis]

Turned out to be quite simple #1177