Fixed minor typo (#178)

* Corrected minor typo

vsvarsall is not a valid command, even the page hyperlinked to is using vcvarsall.

* Fixed minor typo

Had the line modified written as vsvarsall instead of vcvarsall. I don't believe that the command was ever named vsvarsall due to the fact that the webpage you linked to names it vcvarsall

Author: NovaSmoof

README.md

@@ -304,9 +304,9 @@ CMake will detect which compiler was used to build each of the Conan targets. If
 				[Environment]::SetEnvironmentVariable("CXX", "cl.exe", "User")
 				refreshenv
 
-		  Set the architecture using [vsvarsall](https://docs.microsoft.com/en-us/cpp/build/building-on-the-command-line?view=vs-2019#vcvarsall-syntax):
+		  Set the architecture using [vcvarsall](https://docs.microsoft.com/en-us/cpp/build/building-on-the-command-line?view=vs-2019#vcvarsall-syntax):
 
-				vsvarsall.bat x64
+				vcvarsall.bat x64
 
 		- clang