Updated StreamField blocks API (markdown)

StreamField-blocks-API.md

@@ -213,4 +213,11 @@ Return the Javascript parameter list (a string consisting of zero or more JS exp
 
 ### default
 
-The default value for blocks of this type; used as the initial value for newly-created instances of this block. For our shopping list, this is `[]`.
+The default value for blocks of this type; used as the initial value for newly-created instances of this block. For our shopping list, this is `[]`.
+
+## Addendum
+
+Implementation details that should be covered here (but aren't totally set in stone yet):
+
+* Javascript API refactor - rather than two levels of indirection (meta-initialiser and initialiser), there's just an initialiser function that takes js_declaration_param and prefix as its two parameters
+* BoundBlock as a helper; calls to js_declaration_param should be done as block_factory.bind(val, prefix).js_declaration_param() rather than block_factory.js_declaration_param(val) so that blocks can potentially subclass BoundBlock to carry extra data around