data directory configuration, airblade/vim-rooter and CWD

[MagicDuck]

Hi there,

Thank you for the great plugin!
Just wanted to mention a part of the config that was tricky for me and If you are ok with it I can create a PR to update the README:

In the README's data directory configuration section it says to do something like the following to get the project name:

local project_name = vim.fn.fnamemodify(vim.fn.getcwd(), ':p:h:t')

In my case, I was using the airblade/vim-rooter plugin, which automatically changes the cwd upon navigation to a file, and vim.fn.getcwd() was returning the "wrong" value before the cwd had been changed.
The solution I came up with was to use the same construct that's used for the root_dir prop:

local project_root = require("jdtls.setup").find_root({"gradlew"})
local project_name = vim.fn.fnamemodify(project_root, ":p:h:t")

This feels more bulletproof than using vim.fn.getcwd().

Also, another side thing was that the build.gradle for the project I was working on relied on the cwd being correct as it was reading some relative files, and it took me a while to realize I had to set cmd_cwd = project_root.

Cheers,
Stephan