feat: image and link parser (#1744)

* feat: image and link parser

* chore: update

plugin/gomark/parser/image.go

@@ -0,0 +1,55 @@
+package parser
+
+import "github.com/usememos/memos/plugin/gomark/parser/tokenizer"
+
+type ImageParser struct {
+	AltText string
+	URL     string
+}
+
+func NewImageParser() *ImageParser {
+	return &ImageParser{}
+}
+
+func (*ImageParser) Match(tokens []*tokenizer.Token) *ImageParser {
+	if len(tokens) < 5 {
+		return nil
+	}
+	if tokens[0].Type != tokenizer.ExclamationMark {
+		return nil
+	}
+	if tokens[1].Type != tokenizer.LeftSquareBracket {
+		return nil
+	}
+	cursor, altText := 2, ""
+	for ; cursor < len(tokens)-2; cursor++ {
+		if tokens[cursor].Type == tokenizer.Newline {
+			return nil
+		}
+		if tokens[cursor].Type == tokenizer.RightSquareBracket {
+			break
+		}
+		altText += tokens[cursor].Value
+	}
+	if tokens[cursor+1].Type != tokenizer.LeftParenthesis {
+		return nil
+	}
+	matched, url := false, ""
+	for _, token := range tokens[cursor+2:] {
+		if token.Type == tokenizer.Newline || token.Type == tokenizer.Space {
+			return nil
+		}
+		if token.Type == tokenizer.RightParenthesis {
+			matched = true
+			break
+		}
+		url += token.Value
+	}
+	if !matched || url == "" {
+		return nil
+	}
+	return &ImageParser{
+		AltText: altText,
+		URL:     url,
+	}
+}