add type declaration file

[kamiazya]

What was a problem

The lack of type definitions made it difficult to operate plugins from the API.

How this PR fixes the problem

Added a type definition file so that completion etc. can be heard.

Check lists (check x in [ ] of list items)

• Test passed
• Coding style (indentation, etc)

Additional Comments (if any)

fix #12

[kamiazya]

@safareli Hi,

As you commented in issue #12, I added the type definition, but can you confirm that the type definition you want is output?

You can check the type by specifying as follows.
(Since there is no built JS file, it doesn't actually work)

"dependencies": {
  ...,
  "prettier-plugin-dot": "ts-graphviz/prettier-plugin-dot#add-type-declaration-file",
  ...
},

---

If you need an API type definition like the printXxx function, I will consider it, so please tell us what you want to do.

[safareli]

In terms of typing this is what I was looking for. Thanks!

[kamiazya]

@all-contributors please add @safareli for ideas

[allcontributors]

@kamiazya

I've put up a pull request to add @safareli! 🎉