Adds comprehensive README documentation (#70)

* Adds comprehensive README documentation

Introduces a detailed README file to provide users with a comprehensive guide to the Speechmatics Python SDK.

The README includes:
- Quick start instructions for installation and basic usage
- Information on key features, use cases, and integration examples
- Documentation links and migration guides
- Information about Speechmatics technology
- Links to resources and community support

* Removes bold formatting from migration guide links

Updates the README to remove bold formatting from the "Full Migration Guides" section.
This improves the visual consistency of the document and avoids unnecessary emphasis on the links.

* Updates examples and adds env variable

Refactors the examples in the README to use environment variables
for the API key and includes an async close on the client in the
batch example. Also adds prefer_current_speaker to the speaker
diarization config example.

* Updates README with usage examples and features

Enhances the README with detailed examples for batch,
realtime, TTS, and voice agent functionalities.

Also, includes installation instructions, key features,
and use cases for the Speechmatics Python SDK.

* Fixed broken status page link to README

* Enhances README with examples and details

Updates the README to include more detailed examples for batch transcription, realtime streaming, text-to-speech, and voice agent functionalities.

Adds sections on key features like speaker diarization, custom dictionaries, audio intelligence, and translation with corresponding code snippets.

Provides information on framework integrations, focusing on LiveKit Agents and Pipecat AI, improving user understanding and adoption.

Author: Zultran