Allow users to add packages to the end of `PATH` in the neovim wrapper.
This is useful for LSP versions that might need to be overriden based on
the environment, e.g. `haskell-language-server` versions provided by a
project's devshell.
The official method for obtaining the generated initRc content is from
wrapped neovim rather than from makeNeovimConfig helper. To use this
approach: first wrap neovim with the generated config, then override it
with our wrapperArgs.
The motivation for this change was to avoid generating empty
config sections like
vim.cmd([[
]])
To make a config generation cleaner several helper functions introduced:
* `hasContent` have been moved to helpers
* `concatNonEmptyLines` joins strings (which has content) separated with
newlines
* `wrapVimscriptForLua` wraps a lua string for using in Vimscript, but
only if the string has content, otherwise empty string is returned
* `wrapLuaForVimscript` wraps Vimscript for using in lua, but only if
the string has content, otherwise empty string is returned
Added tests:
* testing that all possible config sections are present in the final
generated config
* testing that the config files generated by empty `files` definitions
don't have any content in it
