docs: add README badges (#4)

Add README badges to show the status of the project. Also, revamp the
README header section to center the header content.

README.md

@@ -1,9 +1,29 @@
-# SGHI ETL Core
-
-[![Checked with pyright](https://microsoft.github.io/pyright/img/pyright_badge.svg)](https://microsoft.github.io/pyright/)
-[![Ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff)
-[![pre-commit](https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white)](https://github.com/pre-commit/pre-commit)
-[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://github.com/savannahghi/sghi-etl-core/blob/main/LICENSE)
+<h1 align="center" style="border-bottom: none; text-align: center;">SGHI ETL Core</h1>
+<h3 align="center" style="text-align: center;">API specification for components of a simple ETL workflow.</h3>
+<p align="center" style="text-align: center;">
+    <a href="https://microsoft.github.io/pyright/">
+        <img alt="Checked with pyright" src="https://microsoft.github.io/pyright/img/pyright_badge.svg">
+    </a>
+    <a href="https://github.com/astral-sh/ruff">
+        <img alt="Ruff" src="https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json">
+    </a>
+    <a href="https://github.com/pre-commit/pre-commit">
+        <img alt="pre-commit" src="https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white">
+    </a>
+    <a href="https://github.com/savannahghi/sghi-etl-core/blob/main/LICENSE">
+        <img alt="GitHub License" src="https://img.shields.io/badge/License-MIT-blue.svg">
+    </a>
+</p>
+<p align="center" style="text-align: center;">
+    <a href="https://github.com/savannahghi/sghi-etl-core/actions/workflows/ci.yml">
+        <img alt="CI" src="https://github.com/savannahghi/sghi-etl-core/actions/workflows/ci.yml/badge.svg">
+    </a>
+    <a href="https://coveralls.io/github/savannahghi/sghi-etl-core?branch=main">
+        <img alt="Coverage Status" src="https://coveralls.io/repos/github/savannahghi/sghi-etl-core/badge.svg?branch=main">
+    </a>
+</p>
+
+---
 
 `sghi-etl-core` specifies the API of simple ETL workflows. That is, this
 project defines and specifies the interfaces of the main components needed to