Add conan profile detect command to README

This is required by conan.

Author: albaropereyra22

README.md

@@ -56,6 +56,7 @@ The JsonCpp port in vcpkg is kept up to date by Microsoft team members and commu
 
 You can download and install JsonCpp using the [Conan](https://conan.io/) package manager:
 
+    conan profile detect
     conan install -r conancenter --requires="jsoncpp/[*]" --build=missing
 
 The JsonCpp package in Conan Center is kept up to date by [ConanCenterIndex](https://github.com/conan-io/conan-center-index) contributors. If the version is out of date, please create an issue or pull request on the Conan Center Index repository.