(CHANGELOG) fixed some details [skip-ci]

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to the Koopa will be documented in this file.
 
 ## 0.0.2 - 2021-12-24
 
-# Added
+### Added
 
 * More re-imports.
 * Example `opt`, `brainfuck` and `interpreter`.
@@ -13,14 +13,14 @@ All notable changes to the Koopa will be documented in this file.
 * Method `Generator::new_with_visitor` for visitors that has internal state.
 * `ValueCursorMut` for instruction list in basic blocks.
 
-# Changed
+### Changed
 
 * Replaced all `debug_assert`s with `assert`s.
 * Removed all unary operations.
 * Signature of method `Driver::from_path` and `Generator::from_path`.
 * Signature of method `Value::replace_all_uses_with`.
 
-# Fixed
+### Fixed
 
 * Fault about generating branch instructions into LLVM IR.
 * Fault about creating file in `Generator::from_path`.