Added triple licensing details (#68)

Author: james-2001

README.md

@@ -98,11 +98,18 @@ managed in the future.
 
 # License
 
-This project is licensed under the Apache 2.0 license with the LLVM exception.
-See [LICENSE](LICENSE) for more details.
+This project is triple licenced under the Apache 2/ Apache 2 with LLVM exceptions/ MIT licences. The reasoning for this is:
+- Apache 2/ MIT is common in the rust ecosystem.
+- Apache 2/ MIT is used in the rust standard library, and some of this code may be migrated there.
+- Some of this code may be used in compiler output, and the Apache 2 with LLVM exceptions licence is useful for this.
+
+For more details see 
+- [Apache 2 Licence](LICENSE-APACHE)
+- [Apache 2 Licence with LLVM exceptions](LICENSE-Apache-2.0_WITH_LLVM-exception)
+- [MIT Licence](LICENSE-MIT)
 
 ### Contribution
 
 Unless you explicitly state otherwise, any contribution intentionally submitted
-for inclusion in this project by you, as defined in the Apache-2.0 license,
+for inclusion in this project by you, as defined in the Apache 2/ Apache 2 with LLVM exceptions/ MIT licenses,
 shall be licensed as above, without any additional terms or conditions.