Add FFI example (#2037)

* Add FFI example

* Remove unnecessary dependency (libc)

* Tweak python example and add CI
CI Tweak; separate task for ffi-example run

* Remove OnceCell dep; use std

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Co-authored-by: wassimans <wassim@wassimans.com>

examples/ffi-example/.gitignore

@@ -0,0 +1,10 @@
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+db.sqlite
+db.sqlite-shm
+db.sqlite-wal
+.tool-versions
+
+/target
+/build
+/node_modules