docs: Add documentation for GitHub Actions and Docker image builds

docs/github-actions.md

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+# GitHub Actions for Docker Image Builds
+
+This document explains how GitHub Actions are used in this project to automate the building and pushing of Docker images. The project uses two main workflows: one for building the base image and another for building the resulting image.
+
+## Building the Base Image
+
+The base image is built using a separate workflow defined in `.github/workflows/base-image.yml`. This workflow is responsible for creating a foundational Docker image that other images can build upon. The base image is defined in `base_image/Dockerfile`.
+
+### Key Steps in Base Image Workflow
+
+1. **Checkout Code**: The workflow checks out the code from the repository to access the Dockerfile and any necessary scripts.
+2. **Set Up Docker**: It sets up Docker Buildx, which is a Docker CLI plugin for extended build capabilities with BuildKit.
+3. **Build and Push**: The base image is built using the instructions in `base_image/Dockerfile` and pushed to a Docker registry.
+
+### Usage of Base Image
+
+The base image serves as a starting point for the main Docker image. It includes essential dependencies and configurations that are common across different builds, ensuring consistency and reducing build times for the resulting images.
+
+## Building the Resulting Image
+
+The main workflow for building the resulting Docker image is defined in `.github/workflows/main.yml`. This workflow is triggered on pushes and pull requests to the `main` and `develop` branches.
+
+### Key Steps in Main Workflow
+
+1. **Initial Notification**: Sends a Slack notification indicating the start of the Docker image creation process.
+2. **Create Docker Tag**: Uses the Docker metadata action to generate tags for the Docker image based on the branch or tag being built.
+3. **Build and Push**: Builds the Docker image using `Dockerfile` and pushes it to the Docker registry. This step supports parallel builds for different platforms (e.g., `linux/amd64`, `linux/arm64`).
+4. **Comment on Pull Request**: If the workflow is triggered by a pull request, it comments on the PR with the Docker image tags and labels.
+5. **Final Notification**: Sends a Slack notification indicating the completion of the Docker image creation process.
+
+### Parallel Builds in Dockerfile
+
+The `Dockerfile` supports parallel builds by specifying multiple stages for different components. Each stage is responsible for building a specific part of the application, such as:
+
+- **R-scape**: Installs R-scape, a tool for RNA sequence analysis.
+- **tRNAScan-SE**: Installs tRNAScan-SE, a tool for identifying tRNA genes.
+- **Bio-Easel**: Installs Bio-Easel, a library for biological sequence analysis.
+- **Traveler**: Installs Traveler, a tool for RNA structure visualization.
+- **Scripts**: Installs various scripts for RNA analysis.
+- **Ribovore-Infernal-Easel**: Installs Ribovore and Infernal, tools for RNA sequence analysis.
+- **RNArtist**: Installs RNArtist, a tool for RNA structure visualization.
+
+These stages are combined in the final build stage to create a comprehensive Docker image that includes all necessary tools and dependencies.
+
+### Parallel Builds in Main Workflow
+
+The main workflow supports parallel builds for multiple platforms using Docker Buildx. This allows the resulting Docker image to be compatible with different architectures, enhancing its usability across various environments.
+
+By automating these processes with GitHub Actions, the project ensures consistent and efficient Docker image builds, reducing manual effort and potential errors.