feat: format markdown in changelog entry (#41)

internal/markdown/prettier.go

@@ -0,0 +1,31 @@
+package markdown
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+)
+
+type newLineTransformer struct{}
+
+var _ parser.ASTTransformer = (*newLineTransformer)(nil) // interface compliance
+
+func (t *newLineTransformer) Transform(doc *ast.Document, _ text.Reader, _ parser.Context) {
+	// No error can happen as they can only come from the walker function
+	_ = ast.Walk(doc, func(node ast.Node, entering bool) (ast.WalkStatus, error) {
+		if !entering || node.Type() != ast.TypeBlock {
+			return ast.WalkContinue, nil
+		}
+
+		switch node.Kind() {
+		case ast.KindListItem:
+			// Do not add empty lines between every list item
+			break
+		default:
+			// Add empty lines between every other block
+			node.SetBlankPreviousLines(true)
+		}
+
+		return ast.WalkContinue, nil
+	})
+}