Added Superscript and Subscript formats

Author: dchenk

README.md

@@ -30,6 +30,7 @@ fmt.Println(string(html))
  - Italic
  - Link
  - Strikethrough
+ - Superscript/Subscript
  - Underline
 
 ### Block

inline_formats.go

@@ -139,3 +139,20 @@ func (bf *bkgFormat) Fmt() *Format {
 func (*bkgFormat) HasFormat(o *Op) bool {
 	return o.HasAttr("background")
 }
+
+// script (sup and sub)
+
+type scriptFormat struct {
+	t string
+}
+
+func (sf *scriptFormat) Fmt() *Format {
+	return &Format{
+		Val:   sf.t,
+		Place: Tag,
+	}
+}
+
+func (*scriptFormat) HasFormat(o *Op) bool {
+	return o.HasAttr("script")
+}

render.go

@@ -360,6 +360,14 @@ func (o *Op) getFormatter(keyword string, customFormats func(string, *Op) Format
 		return &bkgFormat{
 			c: o.Attrs["background"],
 		}
+	case "script":
+		sf := new(scriptFormat)
+		if o.Attrs["script"] == "super" {
+			sf.t = "sup"
+		} else {
+			sf.t = "sub"
+		}
+		return sf
 	}
 
 	return nil

render_test.go

@@ -21,6 +21,8 @@ func TestSimple(t *testing.T) {
 		`[{"insert":"text "},{"insert":{"image":"source-url"}},{"insert":" more text\n"}]`,                               // image
 		`[{"insert":"abc "},{"attributes":{"background":"#66a3e0"},"insert":"colored"},{"insert":" plain\n"}]`,           // background
 		`[{"attributes":{"underline":true},"insert":"underlined"},{"insert":"\n"}]`,                                      // underlined
+		`[{"insert":"plain"},{"attributes":{"script":"super"},"insert":"super"},{"insert":"\n"}]`,                        // superscript
+		`[{"insert":"plain"},{"attributes":{"script":"sub"},"insert":"sub"},{"insert":"\n"}]`,                            // subscript
 	}
 
 	want := []string{
@@ -35,6 +37,8 @@ func TestSimple(t *testing.T) {
 		`<p>text <img src="source-url"> more text</p>`,
 		`<p>abc <span style="background-color:#66a3e0;">colored</span> plain</p>`,
 		"<p><u>underlined</u></p>",
+		"<p>plain<sup>super</sup></p>",
+		"<p>plain<sub>sub</sub></p>",
 	}
 
 	for i := range cases {