docs: Update quickstart page to structure things a little more for the novices (#1873)

# What does this PR do?
Another doc enhancement for
https://github.com/meta-llama/llama-stack/issues/1818

Summary of changes:
- `docs/source/distributions/configuration.md`
   - Updated dropdown title to include a more user-friendly description.

- `docs/_static/css/my_theme.css`
   - Added styling for `<h3>` elements to set a normal font weight.

- `docs/source/distributions/starting_llama_stack_server.md`
- Changed section headers from bold text to proper markdown headers
(e.g., `##`).
- Improved descriptions for starting Llama Stack server using different
methods (library, container, conda, Kubernetes).
- Enhanced clarity and structure by converting instructions into
markdown headers and improved formatting.

- `docs/source/getting_started/index.md`
   - Major restructuring of the "Quick Start" guide:
- Added new introductory section for Llama Stack and its capabilities.
- Reorganized steps into clearer subsections with proper markdown
headers.
- Replaced dropdowns with tabbed content for OS-specific instructions.
- Added detailed steps for setting up and running the Llama Stack server
and client.
- Introduced new sections for running basic inference and building
agents.
- Enhanced readability and visual structure with emojis, admonitions,
and examples.

- `docs/source/providers/index.md`
   - Updated the list of LLM inference providers to include "Ollama."
   - Expanded the list of vector databases to include "SQLite-Vec."

Let me know if you need further details!

## Test Plan
Renders locally, included screenshot.

# Documentation

For https://github.com/meta-llama/llama-stack/issues/1818

<img width="1332" alt="Screenshot 2025-04-09 at 11 07 12 AM"
src="https://github.com/user-attachments/assets/c106efb9-076c-4059-a4e0-a30fa738585b"
/>

---------

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

docs/source/distributions/starting_llama_stack_server.md

@@ -2,22 +2,22 @@
 
 You can run a Llama Stack server in one of the following ways:
 
-**As a Library**:
+## As a Library:
 
 This is the simplest way to get started. Using Llama Stack as a library means you do not need to start a server. This is especially useful when you are not running inference locally and relying on an external inference service (eg. fireworks, together, groq, etc.) See [Using Llama Stack as a Library](importing_as_library)
 
 
-**Container**:
+## Container:
 
 Another simple way to start interacting with Llama Stack is to just spin up a container (via Docker or Podman) which is pre-built with all the providers you need. We provide a number of pre-built images so you can start a Llama Stack server instantly. You can also build your own custom container. Which distribution to choose depends on the hardware you have. See [Selection of a Distribution](selection) for more details.
 
 
-**Conda**:
+## Conda:
 
 If you have a custom or an advanced setup or you are developing on Llama Stack you can also build a custom Llama Stack server. Using `llama stack build` and `llama stack run` you can build/run a custom Llama Stack server containing the exact combination of providers you wish. We have also provided various templates to make getting started easier. See [Building a Custom Distribution](building_distro) for more details.
 
 
-**Kubernetes**:
+## Kubernetes:
 
 If you have built a container image and want to deploy it in a Kubernetes cluster instead of starting the Llama Stack server locally. See [Kubernetes Deployment Guide](kubernetes_deployment) for more details.