Add missing platform support docs to sidebar

Also sort sidebar alphabetically by document filename

Author: Michcioperz

src/doc/rustc/src/SUMMARY.md

@@ -15,13 +15,15 @@
 - [Platform Support](platform-support.md)
     - [Template for target-specific documentation](platform-support/TEMPLATE.md)
     - [aarch64-apple-ios-sim](platform-support/aarch64-apple-ios-sim.md)
+    - [aarch64-unknown-none-hermitkernel](platform-support/aarch64-unknown-none-hermitkernel.md)
     - [armv7-unknown-linux-uclibceabi](platform-support/armv7-unknown-linux-uclibceabi.md)
     - [armv7-unknown-linux-uclibceabihf](platform-support/armv7-unknown-linux-uclibceabihf.md)
-    - [aarch64-unknown-none-hermitkernel](platform-support/aarch64-unknown-none-hermitkernel.md)
     - [\*-kmc-solid_\*](platform-support/kmc-solid.md)
+    - [m68k-unknown-linux-gnu](platform-support/m68k-unknown-linux-gnu.md)
+    - [mips64-openwrt-linux-musl](platform-support/mips64-openwrt-linux-musl.md)
     - [*-unknown-openbsd](platform-support/openbsd.md)
-    - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
+    - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
 - [Target Tier Policy](target-tier-policy.md)
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)