docs: Adding Provider sections to docs (#1195)

# What does this PR do?
Adding Provider sections to docs (some of these will be empty and need
updating).


This PR is still a draft while I seek feedback from other contributors.
I opened it to make the structure visible in the linked GitHub Issue.

# Closes https://github.com/meta-llama/llama-stack/issues/1189

- Providers Overview Page
![Screenshot 2025-02-21 at 12 15
09 PM](https://github.com/user-attachments/assets/e83e5a17-0d96-4de0-8251-68161799a054)

- SQLite-Vec specific page
![Screenshot 2025-02-21 at 12 15
34 PM](https://github.com/user-attachments/assets/14773900-fc8f-49e9-832a-b060b7ca010a)

## Test Plan
N/A

[//]: # (## Documentation)

---------

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

docs/source/providers/vector_io/sqlite-vec.md

@@ -0,0 +1,33 @@
+---
+orphan: true
+---
+# SQLite-Vec
+
+[SQLite-Vec](https://github.com/asg017/sqlite-vec) is an inline vector database provider for Llama Stack. It 
+allows you to store and query vectors directly within an SQLite database. 
+That means you're not limited to storing vectors in memory or in a separate service.
+
+## Features
+
+- Lightweight and easy to use
+- Fully integrated with Llama Stack
+
+## Usage
+
+To use SQLite-Vec in your Llama Stack project, follow these steps:
+
+1. Install the necessary dependencies.
+2. Configure your Llama Stack project to use SQLite-Vec.
+3. Start storing and querying vectors.
+
+## Installation
+
+You can install SQLite-Vec using pip:
+
+```bash
+pip install sqlite-vec
+```
+
+## Documentation
+
+See [sqlite-vec's GitHub repo](https://github.com/asg017/sqlite-vec/tree/main) for more details about sqlite-vec in general.