Add comments to metadata

Closes # 17

meta.go

@@ -48,7 +48,8 @@ func ParseMeta (input string) (Meta, error) {
 	meta := make(Meta)
 	for _, line := range strings.Split(input, "\n") {
 		line = strings.TrimSpace(line)
-		if line == "" { continue }
+		if line == ""                   { continue }
+		if strings.HasPrefix(line, "#") { continue }
 		key, value, ok := strings.Cut(line, ":")
 		if !ok {
 			return nil, ErrMetaMalformed

meta_test.go

@@ -20,6 +20,8 @@ FOO: baR
 Shouldn't break anything: ---
 
 this :  that
+# a comment
+  #also a comment
 Sentence: ` + quickBrownFox + `
 ---
 ` + correctBody)