Add readme

README.md

 # jdk-macos-legacy
+
+Patches for OpenJDK to create builds for Mac OS X 10.6 and later.
+
+## Supported versions
+| JDK Version | Minimum macOS version | Notes | Latest Build|
+|-------------|-----------------------|-------|-------------|
+| 1.8 (LTS)   | Mac OS X 10.6         |       | Soon:tm:    |
+| 11 (LTS)    | Mac OS X 10.6         |       | Soon:tm:    |
+| 17 (LTS)    | OS X 10.8             |       | Soon:tm:    |
+| 21 (LTS)    | OS X 10.8             |       | Soon:tm:    |
+| 22          | OS X 10.8             |       | Soon:tm:    |
+
+## Prebuilt releases
+Builds of the OpenJDK are compiled from release tags on a regular basis. These builds are available for download from the [releases page](https://github.com/Jazzzny/jdk-macos-legacy/releases) of this repository. If you need a build for a specific version of the JDK (i.e. 1.8), you can find it in the "Latest Build" column of the table above.
+
+## Building
+1. Clone this repository
+2. Apply the patch files (located in the patches/`version number` folders) to the OpenJDK source code for the version you want to build
+3. Follow the build instructions for OpenJDK
+
+## License
+This project is licensed under the GPL v2 license. For more information, see the [LICENSE](LICENSE) file.
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