Add batch file to sign main executables

All future releases of UIforETW will have the two main executables
signed. This is particularly important since these two are run as
administrator.

SHA1 signing is currently not used because it does not seem to add any
value for the operating systems (Windows 7 and above, and maybe Windows
Vista, but probably not) that UIforETW targets. If SHA1 is needed I can
add it - but I hate having to type the signing-key password twice.

SignBinaries.bat

@@ -0,0 +1,19 @@
+@echo off
+set local
+rem Signing pattern taken from:
+rem https://textslashplain.com/2016/01/10/authenticode-in-2016/
+
+rem Add path for signtool
+set path=%path%;C:\Program Files (x86)\Windows Kits\10\bin\x64
+
+rem So far I see no indications that SHA1 signing is actually needed.
+rem signtool sign /d "UIforETW" /du "https://github.com/google/UIforETW/releases" /n "Bruce Dawson" /tr http://timestamp.digicert.com /fd SHA1 %~dp0bin\UIforETW.exe %~dp0bin\UIforETW32.exe
+rem @if not %errorlevel% equ 0 goto failure
+
+rem Sign both 64-bit and 32-bit versions of UIforETW with the same description.
+signtool sign /d "UIforETW" /du "https://github.com/google/UIforETW/releases" /n "Bruce Dawson" /tr http://timestamp.digicert.com /td SHA256 /fd SHA256 %~dp0bin\UIforETW.exe %~dp0bin\UIforETW32.exe
+@if not %errorlevel% equ 0 goto failure
+exit /b
+
+:failure
+echo Signing failed!