plugins/typescript-tools: init + test

[garaiza-93]

Adds typescript-tools: https://github.com/pmizio/typescript-tools.nvim/

Fixes #964

[GaetanLepage]

Thank you for taking a shot at this one :)

[garaiza-93]

Felt right since you're already working on rustacean for me :p

[garaiza-93]

I've added most of the settings. There's a hurdle though.
How could I add handlers without wanting to tear my hair out? Looking at typescript-tools readme it is a list of variables (or attributes in Nix's case). There's a number of supported methods too, and I hope I don't have to add these one-by-one!!

[GaetanLepage]

How could I add handlers without wanting to tear my hair out?

handlers = mkOption {
  type = with helpers.nixvimTypes; nullOr (attrsOf strLuaFn);
  apply = v: helpers.ifNonNull' v (mapAttrs (_: helpers.mkRaw) v);
  default = null;
  description = "...";
  example = {
    "textDocument/publishDiagnostics" = ''
      api.filter_diagnostics(
        -- Ignore 'This may be converted to an async function' diagnostics.
        { 80006 }
      )
    '';
  };
};