docs/wiki.go: replace info.txt with wiki.go

LUCI trigger go test ./... under every go module, a module
without a go file result in an error from go test.

For #3533

Change-Id: I6973e9c5cc904ff4a3ac4ce97a7bbc3d2b6e4eb0
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/642423
Reviewed-by: Hyang-Ah Hana Kim <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
kokoro-CI: kokoro <[email protected]>
Commit-Queue: Hongxiang Jiang <[email protected]>

Author: h9jiang

docs/info.txt

@@ -0,0 +1,6 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package wiki contains the source of the github.com/golang/vscode-go/wiki.
+package wiki