tools, gopls: add pkg.go.dev badges to READMEs

Change-Id: I7f7390048ecd51a7c24c86c65fbc2722fc752270
Reviewed-on: https://go-review.googlesource.com/c/tools/+/275233
Trust: Rebecca Stambler <[email protected]>
Run-TryBot: Rebecca Stambler <[email protected]>
Reviewed-by: Julie Qiu <[email protected]>

Author: stamblerre

README.md

@@ -1,5 +1,7 @@
 # Go Tools
 
+[![PkgGoDev](https://pkg.go.dev/badge/golang.org/x/tools)](https://pkg.go.dev/golang.org/x/tools)
+
 This subrepository holds the source for various packages and tools that support
 the Go programming language.
 

gopls/README.md

@@ -1,5 +1,7 @@
 # gopls documentation
 
+[![PkgGoDev](https://pkg.go.dev/badge/golang.org/x/tools/gopls)](https://pkg.go.dev/golang.org/x/tools/gopls)
+
 gopls (pronounced: "go please") is the official [language server] for the Go language.
 
 ## Status