Caption support (#2462)

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

vendor/github.com/asticode/go-astikit/float.go

@@ -0,0 +1,60 @@
+package astikit
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+)
+
+// Rational represents a rational
+type Rational struct{ den, num int }
+
+// NewRational creates a new rational
+func NewRational(num, den int) *Rational {
+	return &Rational{
+		den: den,
+		num: num,
+	}
+}
+
+// Num returns the rational num
+func (r *Rational) Num() int {
+	return r.num
+}
+
+// Den returns the rational den
+func (r *Rational) Den() int {
+	return r.den
+}
+
+// ToFloat64 returns the rational as a float64
+func (r *Rational) ToFloat64() float64 {
+	return float64(r.num) / float64(r.den)
+}
+
+// MarshalText implements the TextMarshaler interface
+func (r *Rational) MarshalText() (b []byte, err error) {
+	b = []byte(fmt.Sprintf("%d/%d", r.num, r.den))
+	return
+}
+
+// UnmarshalText implements the TextUnmarshaler interface
+func (r *Rational) UnmarshalText(b []byte) (err error) {
+	r.num = 0
+	r.den = 1
+	if len(b) == 0 {
+		return
+	}
+	items := bytes.Split(b, []byte("/"))
+	if r.num, err = strconv.Atoi(string(items[0])); err != nil {
+		err = fmt.Errorf("astikit: atoi of %s failed: %w", string(items[0]), err)
+		return
+	}
+	if len(items) > 1 {
+		if r.den, err = strconv.Atoi(string(items[1])); err != nil {
+			err = fmt.Errorf("astifloat: atoi of %s failed: %w", string(items[1]), err)
+			return
+		}
+	}
+	return
+}