Add vk bridge (#1372)

* Add vk bridge

* Vk bridge attachments

* Vk bridge forwarded messages

* Vk bridge sample config and code cleanup

* Vk bridge add vendor

* Vk bridge message edit

* Vk bridge: fix fetching names of other bots

* Vk bridge: code cleanup

* Vk bridge: fix shadows declaration

* Vk bridge: remove UseFileURL

vendor/github.com/SevereCloud/vksdk/v2/internal/charset.go

@@ -0,0 +1,60 @@
+/*
+Package internal unimportable
+*/
+package internal // import "github.com/SevereCloud/vksdk/v2/internal"
+
+import (
+	"io"
+	"strings"
+
+	"golang.org/x/text/encoding/charmap"
+	"golang.org/x/text/runes"
+	"golang.org/x/text/transform"
+)
+
+// illegal is a collection of runes.
+type illegal struct{}
+
+// Contains return true.
+func (i illegal) Contains(r rune) bool {
+	return !(r == 0x09 ||
+		r == 0x0A ||
+		r == 0x0D ||
+		r >= 0x20 && r <= 0xDF77 ||
+		r >= 0xE000 && r <= 0xFFFD ||
+		r >= 0x10000 && r <= 0x10FFFF)
+}
+
+// XMLSanitizerReader creates an io.Reader that
+// wraps another io.Reader and removes illegal xml
+// characters from the io stream.
+func XMLSanitizerReader(xml io.Reader) io.Reader {
+	var i illegal
+	t := transform.Chain(runes.Remove(i))
+
+	return transform.NewReader(xml, t)
+}
+
+// CharsetUnknownError unknown charset.
+type CharsetUnknownError struct {
+	Name string
+}
+
+// Error returns the message of a CharsetUnknownError.
+func (c *CharsetUnknownError) Error() string {
+	return "unknown charset: " + c.Name
+}
+
+// CharsetReader if non-nil, defines a function to generate
+// charset-conversion readers, converting from the provided
+// non-UTF-8 charset into UTF-8. If CharsetReader is nil or
+// returns an error, parsing stops with an error. One of the
+// the CharsetReader's result values must be non-nil.
+func CharsetReader(charset string, input io.Reader) (io.Reader, error) {
+	switch strings.ToLower(charset) {
+	case "windows-1251":
+		return charmap.Windows1251.NewDecoder().Reader(input), nil
+	default:
+		return nil, &CharsetUnknownError{Name: charset}
+	}
+}