[feature] Enable basic video support (mp4 only) (#1274)

* [feature] basic video support

* fix missing semicolon

* replace text shadow with stacked icons

Co-authored-by: f0x <f0x@cthu.lu>

vendor/github.com/abema/go-mp4/util/io.go

@@ -0,0 +1,30 @@
+package util
+
+import (
+	"bytes"
+	"io"
+)
+
+func ReadString(r io.Reader) (string, error) {
+	b := make([]byte, 1)
+	buf := bytes.NewBuffer(nil)
+	for {
+		if _, err := r.Read(b); err != nil {
+			return "", err
+		}
+		if b[0] == 0 {
+			return buf.String(), nil
+		}
+		buf.Write(b)
+	}
+}
+
+func WriteString(w io.Writer, s string) error {
+	if _, err := w.Write([]byte(s)); err != nil {
+		return err
+	}
+	if _, err := w.Write([]byte{0}); err != nil {
+		return err
+	}
+	return nil
+}

vendor/github.com/abema/go-mp4/util/string.go

@@ -0,0 +1,42 @@
+package util
+
+import (
+	"strconv"
+	"strings"
+	"unicode"
+)
+
+func FormatSignedFixedFloat1616(val int32) string {
+	if val&0xffff == 0 {
+		return strconv.Itoa(int(val >> 16))
+	} else {
+		return strconv.FormatFloat(float64(val)/(1<<16), 'f', 5, 64)
+	}
+}
+
+func FormatUnsignedFixedFloat1616(val uint32) string {
+	if val&0xffff == 0 {
+		return strconv.Itoa(int(val >> 16))
+	} else {
+		return strconv.FormatFloat(float64(val)/(1<<16), 'f', 5, 64)
+	}
+}
+
+func FormatSignedFixedFloat88(val int16) string {
+	if val&0xff == 0 {
+		return strconv.Itoa(int(val >> 8))
+	} else {
+		return strconv.FormatFloat(float64(val)/(1<<8), 'f', 3, 32)
+	}
+}
+
+func EscapeUnprintable(r rune) rune {
+	if unicode.IsGraphic(r) {
+		return r
+	}
+	return rune('.')
+}
+
+func EscapeUnprintables(src string) string {
+	return strings.Map(EscapeUnprintable, src)
+}