Fix parsing of list item lines

According to section 5.5.2 of the Gemini specification (v0.16.1), the
space is mandatory.

text.go

@@ -125,8 +125,8 @@ func ParseLines(r io.Reader, handler func(Line)) error {
 				name = strings.TrimLeft(name, spacetab)
 				line = LineLink{url, name}
 			}
-		} else if strings.HasPrefix(text, "*") {
-			text = text[1:]
+		} else if strings.HasPrefix(text, "* ") {
+			text = text[2:]
 			text = strings.TrimLeft(text, spacetab)
 			line = LineListItem(text)
 		} else if strings.HasPrefix(text, "###") {