Soong: Add documentation to sh_binary[_host] module.

Synopsis was missing to the sh_binary[_host] module.

Bug: b/128337482
Test: Ran m soong_docs and verified that sh_binary[_host] module
had a synopsis.

Change-Id: I0bb702ab2d8e4168664e7bba397e0e26af7f03ab

android/sh_binary.go

@@ -123,6 +123,8 @@ func InitShBinaryModule(s *ShBinary) {
 	s.AddProperties(&s.properties)
 }
 
+// sh_binary is for a shell script or batch file to be installed as an
+// executable binary to <partition>/bin.
 func ShBinaryFactory() Module {
 	module := &ShBinary{}
 	InitShBinaryModule(module)
@@ -130,6 +132,8 @@ func ShBinaryFactory() Module {
 	return module
 }
 
+// sh_binary_host is for a shell script to be installed as an executable binary
+// to $(HOST_OUT)/bin.
 func ShBinaryHostFactory() Module {
 	module := &ShBinary{}
 	InitShBinaryModule(module)