move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/gen/_template/client.tmpl

@@ -0,0 +1,27 @@
+{{ define "client" }}
+{{ $pkg := $.Package }}
+{{ template "header" $ }}
+
+// Invoker can invoke raw MTProto rpc calls.
+type Invoker interface {
+  Invoke(ctx context.Context, input bin.Encoder, output bin.Decoder) error
+}
+
+// Client implement methods for calling functions from TL schema via Invoker.
+type Client struct {
+  rpc Invoker
+}
+
+// Invoker returns Invoker used by this client.
+func (c *Client) Invoker() Invoker {
+    return c.rpc
+}
+
+// NewClient creates new Client.
+func NewClient(invoker Invoker) *Client {
+  return &Client{
+    rpc: invoker,
+  }
+}
+
+{{ end }}