Update changelog for #72 and #73

Author: phil-opp

Changelog.md

@@ -1,3 +1,6 @@
+- **Breaking**: Parse bootloader configuration from kernel's Cargo.toml ([#73](https://github.com/rust-osdev/bootloader/pull/73))
+    - At least version 0.7.7 of `bootimage` is required now.
+- Configurable kernel stack size, better non-x86_64 errors ([#72](https://github.com/rust-osdev/bootloader/pull/72))
 - Dynamically map kernel stack, boot info, physical memory and recursive table ([#71](https://github.com/rust-osdev/bootloader/pull/71))
 
 # 0.7.1