Create RELEASE.md for v0.30 (#218)

* Create RELEASE.md for v0.30

* Removed "## New Contributors" section.

RELEASE.md

@@ -0,0 +1,14 @@
+Release Notes for v0.30
+
+## What's Changed
+* Avoid breakages for WITH_LLVM builds with libprotobuf < 3.19.0 by @dhoekwater in https://github.com/google/autofdo/pull/200
+* Fixed testcase failures when build directory is not under the source directory by @shenhanc78 in https://github.com/google/autofdo/pull/206
+* Fix compilation error when building using github build bot. by @shenhanc78 in https://github.com/google/autofdo/pull/210
+* Removed WITH_LLVM and replaced protobuf_generate_cpp with more modern protobuf_generate by @shenhanc78 in https://github.com/google/autofdo/pull/199
+* Fix format/indention error in README. by @shenhanc78 in https://github.com/google/autofdo/pull/212
+* Add a config to build and run on PRs. by @snehasish in https://github.com/google/autofdo/pull/213
+* Update README.md by @snehasish in https://github.com/google/autofdo/pull/214
+* Add a workflow to create release build. by @shenhanc78 in https://github.com/google/autofdo/pull/217
+* Build full-static LLVM tools binaries by @shenhanc78 in https://github.com/google/autofdo/pull/216
+
+**Full Changelog**: https://github.com/google/autofdo/compare/v0.20.1...v0.30