better class comment + key as subclassresponsibility

src/Microdown/MicAnnotationBlock.class.st

@@ -1,14 +1,28 @@
 "
 I represent an annotation, a tag with parameters, delimited by `{!` and `!}`.
+I'm composed of a tag and a list of valued keys following the syntax `tag|key1=value1&key2=value2`
 
 The following example is a citation annotation with the name variable bound to the string 'Duca99a' as a parameter.
 
 ```text
-{!citation|name=Duca99a!}
+{!citation|ref=Duca99a!}
 ```
 
 ```
-MicrodownParser parse: '{!citation|name=Duca99a!}'
+MicrodownParser parse: '{!citation|ref=Duca99a!}'
+```
+
+Note that the first key (that should be defined on the class side via the key method) can be omitted.
+So 
+
+```text
+{!citation|ref=Duca99a!}
+```
+
+is equivalent to 
+
+```text
+{!citation|Duca99a!}
 ```
 "
 Class {
@@ -64,6 +78,13 @@ MicAnnotationBlock class >> parse: delimiter stream: aTokenStream for: aParser [
 		  arguments: arguments
 ]
 
+{ #category : 'parsing' }
+MicAnnotationBlock class >> tag [
+	"Return the identifier of annotation e.g. tag in tag|key=value"
+
+	^ self subclassResponsibility 
+]
+
 { #category : 'visiting' }
 MicAnnotationBlock >> accept: aVisitor [
 	^ aVisitor visitAnnotation: self

src/Microdown/MicCitationBlock.class.st

@@ -16,6 +16,8 @@ Class {
 
 { #category : 'accessing' }
 MicCitationBlock class >> key [
+	"The key for citation|ref=Value is ref"
+
 	^ 'ref'
 ]