Add documentation about supported hashing algorithms (#32)

* Add documentation on inputs page about hashing algorithms

* Add documentation about hashing algorithms to README

README.md

@@ -153,16 +153,16 @@ files-catalog: ${{ github.workspace }}\catalog.txt
 
 ### Digest Algorithm
 ```yaml
-# The name of the digest algorithm used for hashing the file being signed. The default value is SHA256.
-file-digest: SHA384
+# The name of the digest algorithm used for hashing the file being signed. The supported values are SHA256, SHA384, and SHA512. The default value is SHA256.
+file-digest: SHA256
 ```
 
 ### Timestamping
 ```yaml
 # A URL to an RFC3161 compliant timestamping service.
 timestamp-rfc3161: http://timestamp.acs.microsoft.com
 
-# The name of the digest algorithm used for timestamping.
+# The name of the digest algorithm used for timestamping. The supported values are SHA256, SHA384, and SHA512.
 timestamp-digest: SHA256
 ```
 

action.yml

@@ -63,15 +63,17 @@ inputs:
                  a separate line. Can be combined with the files-folder input.
     required: false
   file-digest:
-    description: The name of the digest algorithm used for hashing the files being signed (e.g. SHA256).
+    description: The name of the digest algorithm used for hashing the files being signed. The supported
+                 values are SHA256, SHA384, and SHA512.
     required: false
     default: 'SHA256'
   timestamp-rfc3161:
     description: A URL to an RFC3161 compliant timestamping service.
     required: false
     default: 'http://timestamp.acs.microsoft.com'
   timestamp-digest:
-    description: The name of the digest algorithm used for timestamping.
+    description: The name of the digest algorithm used for timestamping. The supported values are SHA256,
+                 SHA384, and SHA512.
     required: false
     default: 'SHA256'
   append-signature: