Readme: Add OBSWebSocketAHK to Client libraries

[5ony]

Description

Add OBSWebSocketAHK to Client libraries in Readme

Motivation and Context

OBSWebSocketAHK library makes it possible to control OBS via WebSocket from AutoHotKey, which is a free, open-source macro-creation and automation software for Windows.

How Has This Been Tested?

This is a readme change, no need for testing. (However, OBSWebSocketAHK was tested daily by me and their users.)

Types of changes

Documentation change (a change to documentation pages)

Checklist:

• I have read the Contributing Guidelines.
• All commit messages are properly formatted and commits squashed where appropriate.
• My code is not on master or a release/* branch.
• The code has been tested.
• I have included updates to all appropriate documentation.

[tt2468]

I can merge this as-is if you'd like, though I think this might be better located in the Client Software section?

[5ony]

It is more like a library which by in itself do not have any client-like functionality, but provides an API between OBS and AutoHotKey scripts, so that's the reason for the placement. Thank you!