add readme for the migration tool (#4144)

Co-authored-by: Pantani <Pantani>

ignite/internal/tools/gen-mig-diffs/readme.md

@@ -0,0 +1,64 @@
+<div align="center">
+  <h1> Generate Ignite Migration Diffs </h1>
+</div>
+
+This repository hosts the Chain Scaffold Migration Tool for Ignite CLI, designed to help developers migrate their
+projects from older versions of Ignite to the latest release.
+This tool addresses compatibility and feature alignment as a detailed
+in [Issue #3699](https://github.com/ignite/cli/issues/3699) and implemented
+in [PR #3718](https://github.com/ignite/cli/pull/3718).
+
+The migration tool aims to streamline the update process for projects built with Ignite CLI, ensuring they leverage the
+latest improvements and SDK stack.
+
+#### Features
+
+- Automated migration of chain scaffold files.
+- Detailed comparison and generation of migration differences.
+- Support for multiple versions of chain scaffolds.
+
+## Installation
+
+It is located in the `ignite/internal/tools/gen-mig-diffs`
+directory and made it a standalone project.
+
+To set up this tool in your development environment:
+
+1. Clone the Ignite CLI repository:
+
+```shell
+git clone https://github.com/ignite/cli.git && \
+cd cli/ignite/internal/tools/gen-mig-diffs
+```
+
+2. Install and show usage:
+
+```shell
+go install . && gen-mig-diffs -h
+```
+
+3. Run migration diff tool:
+
+```shell
+gen-mig-diffs --output temp/migs --from v0.27.2 --to v28.3.0
+```
+
+## Usage
+
+```bash
+This tool is used to generate migration diff files for each of ignites scaffold commands
+
+Usage:
+  gen-mig-diffs [flags]
+
+Flags:
+  -f, --from string              Version of Ignite or path to Ignite source code to generate the diff from
+  -h, --help                     help for gen-mig-diffs
+  -o, --output string            Output directory to save the migration document (default "docs/docs/06-migration")
+      --repo-output string       Output path to clone the Ignite repository
+  -s, --repo-source string       Path to Ignite source code repository. Set the source automatically set the cleanup to false
+      --repo-url string          Git URL for the Ignite repository (default "https://github.com/ignite/cli.git")
+      --scaffold-cache string    Path to cache directory
+      --scaffold-output string   Output path to clone the Ignite repository
+  -t, --to string                Version of Ignite or path to Ignite source code to generate the diff to
+```