Update 0001-digest-algorithms.md with parameters

docs/0001-digest-algorithms.md

@@ -9,8 +9,29 @@
 
 This extension is an index of additional digest algorithms. It provides a controlled vocabulary of digest algorithm names that may be used to indicate the given algorithm in `fixity` blocks of OCFL Objects, and links their defining extensions.
 
+## Parameters
+
+* name: blake2b_160
+  * description: Indicates if the blake2b-160 algorithm is used 
+  * type: boolean
+  * default: false
+* name: blake2b_256
+  * description: Indicates if the blake2b-256 algorithm is used 
+  * type: boolean
+  * default: false
+* name: blake2b_384
+  * description: Indicates if the blake2b-384 algorithm is used 
+  * type: boolean
+  * default: false
+* name: sha512_256
+  * description: Indicates if the sha512/256algorithm is used 
+  * type: boolean
+  * default: false
+
 ## Digest Algorithms Defined in Community Extensions
 
+Each parameter corresponds to a JSON identifier compliant version of Digest Algorithm Name used in the table below, and indicates if this algorithm is in use as a consequence of including this extension. As the parameters default to false, only the algorithms used need to be listed in *0001-digest-algorithms.json*. 
+
 | Digest Algorithm Name | Note |
 | --------------------- | ---- |
 | `blake2b-160`         | BLAKE2 digest using the 2B variant (64 bit) with size 160 bits as defined by [RFC7693](https://tools.ietf.org/html/rfc7693). MUST be encoded using hex (base16) encoding [RFC4648](https://tools.ietf.org/html/rfc4648). For example, the `blake2b-160` digest of a zero-length bitstream is `3345524abf6bbe1809449224b5972c41790b6cf2` (40 hex digits long). |