Where to place third-party C source code?

[Jorge Araya Navarro]

Hello!

I was wondering if placing third-party C source code that is used in any 
feature I would like to implement in the Emacs project is "against the rules", 
sort of speak.

I ask because I would like to attempt to integrate tree-sitter (a parser 
generator tool and an incremental parsing library; I'm aware there are a couple 
of projects that gives Emacs lisp bindings for this project, too; I'm just 
wondering how the world could be if this thing was shipped in Vanilla Emacs), 
according to its documentation[1]:

    [...] you can use the library in a larger project by adding one source file 
to the project. This source file needs three directories to be in the include 
path when compiled:

    source file:
    - tree-sitter/lib/src/lib.c 

    include directories: 
    - tree-sitter/lib/src
    - tree-sitter/lib/include
    - tree-sitter/lib/utf8proc

The instructions seem straightforward but reading the docs included with the 
Emacs source code there is no mention wherever this is "fair game" (or not) and 
where should such code be placed

[1]: https://tree-sitter.github.io/tree-sitter/using-parsers