Adding new arm target docs to SUMMARY.md

Author: jonathanpallant

src/doc/rustc/src/SUMMARY.md

@@ -55,6 +55,13 @@
     - [riscv32imac-unknown-xous-elf](platform-support/riscv32imac-unknown-xous-elf.md)
     - [riscv32*-unknown-none-elf](platform-support/riscv32-unknown-none-elf.md)
     - [sparc-unknown-none-elf](./platform-support/sparc-unknown-none-elf.md)
+    - [thumbv6m-none-eabi](./platform-support/thumbv6m-none-eabi.md)
+    - [thumbv7m-none-eabi](./platform-support/thumbv7m-none-eabi.md)
+    - [thumbv7em-none-eabi](./platform-support/thumbv7em-none-eabi.md)
+    - [thumbv7em-none-eabihf](./platform-support/thumbv7em-none-eabihf.md)
+    - [thumbv8m.base-none-eabi](./platform-support/thumbv8m.base-none-eabi.md)
+    - [thumbv8m.main-none-eabi](./platform-support/thumbv8m.main-none-eabi.md)
+    - [thumbv8m.main-none-eabihf](./platform-support/thumbv8m.main-none-eabihf.md)
     - [*-pc-windows-gnullvm](platform-support/pc-windows-gnullvm.md)
     - [\*-nto-qnx-\*](platform-support/nto-qnx.md)
     - [*-unikraft-linux-musl](platform-support/unikraft-linux-musl.md)