feat: add header to CHANGELOG.md (#127)

Author: JoshuaKGoldberg

.release-it.json

@@ -8,6 +8,7 @@
 	},
 	"plugins": {
 		"@release-it/conventional-changelog": {
+			"header": "# Changelog",
 			"infile": "CHANGELOG.md",
 			"preset": "conventionalcommits"
 		}

CHANGELOG.md

@@ -1,18 +1,18 @@
+# Changelog
+
 ## [1.21.0](https://github.com/JoshuaKGoldberg/template-typescript-node-package/compare/v1.20.2...v1.21.0) (2022-12-15)
 
 ### Features
 
 - clear CHANGELOG.md and local Git tags in setup ([#125](https://github.com/JoshuaKGoldberg/template-typescript-node-package/issues/125)) ([9ed5f45](https://github.com/JoshuaKGoldberg/template-typescript-node-package/commit/9ed5f452f1de3841647cfff594676819a3e416e5))
 
-# Changelog
-
-### [1.20.2](https://github.com/JoshuaKGoldberg/template-typescript-node-package/compare/v1.20.1...v1.20.2) (2022-12-15)
+## [1.20.2](https://github.com/JoshuaKGoldberg/template-typescript-node-package/compare/v1.20.1...v1.20.2) (2022-12-15)
 
 ### Bug Fixes
 
 - corrected allcontributors setup import path with fs ([#124](https://github.com/JoshuaKGoldberg/template-typescript-node-package/issues/124)) ([2506907](https://github.com/JoshuaKGoldberg/template-typescript-node-package/commit/25069072073b3b26b039aaf2f6b6dea9cd1cd8b2))
 
-### [1.20.1](https://github.com/JoshuaKGoldberg/template-typescript-node-package/compare/v1.20.0...v1.20.1) (2022-12-15)
+## [1.20.1](https://github.com/JoshuaKGoldberg/template-typescript-node-package/compare/v1.20.0...v1.20.1) (2022-12-15)
 
 ### Bug Fixes