Add quiet input to suppress info-level log output (#898)

## Summary

Adds a new `quiet` input (default: `false`) that suppresses `info`-level
log output when set to `true`. Only warnings and errors are shown.

Contributes to: #868

Author: eifinger

README.md

@@ -125,6 +125,9 @@ Have a look under [Advanced Configuration](#advanced-configuration) for detailed
 
     # Add problem matchers
     add-problem-matchers: "true"
+
+    # Suppress info-level log output. Only warnings and errors are shown
+    quiet: "false"
 ```
 
 ### Outputs

action-types.yml

@@ -56,6 +56,8 @@ inputs:
     type: boolean
   add-problem-matchers:
     type: boolean
+  quiet:
+    type: boolean
   resolution-strategy:
     type: enum
     allowed-values:

action.yml

@@ -86,6 +86,9 @@ inputs:
   add-problem-matchers:
     description: "Add problem matchers."
     default: "true"
+  quiet:
+    description: "Suppress info-level log output. Only warnings and errors are shown."
+    default: "false"
   resolution-strategy:
     description: "Resolution strategy to use when resolving version ranges. 'highest' uses the latest compatible version, 'lowest' uses the oldest compatible version."
     default: "highest"