i-1: First draft of a shared KMP library (#2)

- [x] Exposes a `Greeting` class.
- [x] Exposes a `Greeting` class test.

Co-authored-by: Emil Simeonov <emil@theliberatededge.org>
Reviewed-on: emil/AstrologyLibrary#2

.gitignore

@@ -0,0 +1,14 @@
+*.iml
+.gradle
+.idea
+.DS_Store
+build
+captures
+.externalNativeBuild
+.cxx
+local.properties
+xcuserdata
+.kotlin
+#So we don't accidentally commit our private keys
+*.gpg
+