Add cmake install configurations (#1129)

Summary:
Add some cmake configurations to support cmake install command.

So other cmake based project can depends on yoga by using cmake `find_package` function as follow:

```
find_package(yoga CONFIG REQUIRED)
target_link_libraries(main PRIVATE yoga::yogacore)
```

Resolves https://github.com/facebook/yoga/issues/1057

Pull Request resolved: https://github.com/facebook/yoga/pull/1129

Reviewed By: cortinico

Differential Revision: D40581194

Pulled By: NickGerleman

fbshipit-source-id: 1f67991b31713561cad766d695dae11c6fc78bbf

scripts/yoga-config.cmake.in

@@ -0,0 +1,10 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/yogaTargets.cmake")
+
+check_required_components(yoga)