Add Hover support for VSCode.

[Wither362]

"Hover" is an useful feature that vscode uses. When the mouse hovers on top of a word, it shows up the meaning (tooltips) and useful information for the coder, instead of having to go manually to the tt-wiki.net website and search for the description of a function.

I'm making this a Draft PR because I want to finish all the functions and variable information possible before commiting to the main branch.

Is this a good idea? Do you -Pixel Tony- approve this?

How to use this feature

I added a new file, called hoverData.json, where definitions are stored. It should have a structure similar to this example of the built-in function STORE_PERM:

{
  "STORE_PERM": {
    "title": "STORE_PERM(value, address)",
    "description": "Store value in permanent storage (industries, airports, towns only).",
    "example": "STORE_PERM(1, 4)"
}

this, will look like this in VSCode when the user hovers the mouse over it:

What is the purpose of this PR?

The main reason why I'm doing this is because I wanted to learn how to code NewGRFs, but I can't seem to memorize all the built-in features OpenTTD's code gives me. So, with this Hover Feature, modders can actually see what built-in features there are for them to use them faster and smarter.

[Wither362]

help is appreciated 🙏