doc/test-framework/scorecard: add config file section (#1026)

* doc/test-framework/scorecard: add config file section

Author: AlexNPavel

doc/test-framework/scorecard.md

@@ -36,6 +36,24 @@ use. For example:
 $ operator-sdk scorecard --cr-manifest deploy/crds/app_operator_cr.yaml --csv-path deploy/app_operator-0.0.2.yaml
 ```
 
+## Config File
+
+The scorecard supports the use of a config file instead of or in addition to flags for configuration. By default, the scorecard will look
+for a file called `.osdk-scorecard` with either a `.yaml`, `.json`, or `.toml` file extension. You can also
+specify a different config file with the `--config` flag. The configuration options in the config file match the flags.
+For instance, for the flags `--cr-manifest "deploy/crds/cache_v1alpha1_memcached_cr.yaml" --init-timeout 60 --csv-path "deploy/memcachedoperator.0.0.2.csv.yaml"`, the corresponding yaml config file would contain:
+
+```yaml
+cr-manifest: "deploy/crds/cache_v1alpha1_memcached_cr.yaml"
+init-timeout: 60
+csv-path: "deploy/memcachedoperator.0.0.2.csv.yaml"
+```
+
+The hierarchy of config methods from highest priority to least is: flag->file->default.
+
+The config file support is provided by the `viper` package. For more info on how viper
+configuration works, see [`viper`'s README][viper].
+
 ## What Each Test Does
 
 There are 8 tests the scorecard can run:
@@ -83,4 +101,5 @@ the CSV. This test has a maximum score equal to the number of fields in the stat
 [cli-reference]: ../sdk-cli-reference.md#scorecard
 [writing-tests]: ./writing-e2e-tests.md
 [owned-crds]: https://github.com/operator-framework/operator-lifecycle-manager/blob/master/Documentation/design/building-your-csv.md#owned-crds
-[alm-examples]: https://github.com/operator-framework/operator-lifecycle-manager/blob/master/Documentation/design/building-your-csv.md#crd-templates
+[alm-examples]: https://github.com/operator-framework/operator-lifecycle-manager/blob/master/Documentation/design/building-your-csv.md#crd-templates
+[viper]: https://github.com/spf13/viper/blob/master/README.md