update documentation (#69)

Co-authored-by: dbut2 <dbut2@users.noreply.github.com>

README.md

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+# Shortener
+
+Shortener is a simple URL shortening service written in Go. It provides the ability to create short, memorable links that redirect to longer URLs.
+
+## Prerequisites
+
+To run Shortener, ensure you have the following installed:
+- Go (version 1.21 or newer)
+- Docker (optional)
+
+The application also requires access to a database. The provided `schema.sql` file includes the SQL schema that is compatible with MySQL.
+
+## Building
+
+### Manually
+
+1. Navigate to the `shortener` directory.
+2. Run the Go build command:
+    ```bash
+    go build -o shortener ./cmd/shortener
+    ```
+3. The `shortener` binary will be created in the current directory.
+
+### Using Docker
+
+1. Navigate to the root directory of the project.
+2. Build the Docker image with the following command:
+    ```bash
+    docker build -t shortener -f deployment/Dockerfile .
+    ```
+3. The Docker image tagged as `shortener` will be created.
+
+## Configuration
+
+The application can be configured using the `yaml` files located in the `deployment/configs/` directory. It supports environment-specific configurations:
+
+- `prod.yaml` for production
+- `test.yaml` for testing
+- `dev.yaml` for development
+- `local.yaml` for local development
+
+Adjust the configurations as needed for your environment, such as database credentials, datastore identifiers, or cache settings.
+
+## Running
+
+### Manually
+
+Execute the built binary with the following command:
+```bash
+./shortener
+```
+
+You can set the `ENV` environment variable to load specific configurations:
+```bash
+ENV=local ./shortener
+```
+
+### Using Docker
+
+1. Run the Docker image with the following command:
+    ```bash
+    docker run -p 8080:8080 -e ENV=local shortener
+    ```
+2. The application will be accessible on port `8080`.
+
+## Deployment
+
+Refer to the provided `Dockerfile` in `deployment/` directory for deployment configurations. Update it as necessary to use your base image and desired environment.
+
+## Database Schema
+
+To set up your database, use the `schema.sql` file located in the `deployment/` directory. This file contains the SQL commands to create the necessary tables and sample data.
+
+## License
+
+This project is licensed under the MIT License. See the `LICENSE` file for details.
+```