Add OpenHarmony docs to the summary (#10)

Without this the page will no be visible.

Signed-off-by: Jonathan Schwender <[email protected]>

Author: jschwe

src/SUMMARY.md

@@ -13,6 +13,7 @@
   - [Setting up your environment](hacking/setting-up-your-environment.md)
   - [Troubleshooting your build](hacking/troubleshooting-your-build.md)
   - [Building for Android\*](hacking/building-for-android.md)
+  - [Building for OpenHarmony](hacking/building-for-openharmony.md)
 - [Some basic Rust\*](hacking/some-basic-rust.md)
   - [Cargo and crates\*](hacking/cargo-and-crates.md)
   - [Working on a crate\*](hacking/working-on-a-crate.md)