Add missing options to the README for clarity (#53)

Author: AAraKKe

README.md

@@ -48,6 +48,8 @@ The action has the following parameters:
 | ruby-tracer-version            | The version of datadog-ci Ruby gem to use. Defaults to the latest release.                                                                                                                                                                                                                          | false    |               |
 | go-tracer-version              | The version of Orchestrion to use. Defaults to the latest release.                                                                                                                                                                                                                                  | false    |               |
 | java-instrumented-build-system | If provided, only the specified build systems will be instrumented (allowed values are `gradle`,`maven`,`sbt`,`ant`,`all`). `all` is a special value that instruments every Java process. If this property is not provided, all known build systems will be instrumented (Gradle, Maven, SBT, Ant). | false    |               |
+| cache                          | Enable caching of downloaded tracers.                                                                                                                                                                                                                                                               | false    | true          |
+| print-github-step-summary      | Print a summary of the installed tracers to the GitHub step summary. If set to false, the summary is printed to console instead.                                                                                                                                                                    | false    | true          |
 
 ### Additional configuration