add example dataset annotation, fixed formatting

Added sample code to show an annotation example in the dataset element.  The spacing format in the EML attribute element sample code was also edited.

docs/eml-semantic-annotations-primer.md

@@ -12,13 +12,13 @@ Example EML `attribute` element annotation:
 
 ```
 <attribute id="att.4">
-        <attributeName>pctcov</attributeName>
-        <attributeLabel>percent cover</attributeLabel>
-        <attributeDefinition>The percent ground cover on the field</attributeDefinition>
-        <annotation>
-            <propertyURI label="contains measurements of type">http://ecoinformatics.org/oboe/oboe.1.2/oboe-core.owl#containsMeasurementsOfType</propertyURI>
-            <valueURI label="Plant Cover Percentage">http://purl.dataone.org/odo/ECSO_00001197</valueURI>
-        </annotation>
+    <attributeName>pctcov</attributeName>
+    <attributeLabel>percent cover</attributeLabel>
+    <attributeDefinition>The percent ground cover on the field</attributeDefinition>
+    <annotation>
+        <propertyURI label="contains measurements of type">http://ecoinformatics.org/oboe/oboe.1.2/oboe-core.owl#containsMeasurementsOfType</propertyURI>
+        <valueURI label="Plant Cover Percentage">http://purl.dataone.org/odo/ECSO_00001197</valueURI>
+    </annotation>
 </attribute>
 
 ```
@@ -34,8 +34,28 @@ Example EML `attribute` element annotation:
 
 - describe that this annotation is embedded within an EML `dataset` element and the subject is the `dataset` id attribute value
 - describe the propertyURI and valueURI elements in the annotation, the label attributes of these elements, and the content of these elements  
-- show an example annotation
 
+Example `dataset` annotation:
+
+```
+<dataset id="dataset-01">
+    <title>Data from Cedar Creek LTER on productivity and species richness for use in a workshop titled 
+    "An Analysis of the Relationship between Productivity and Diversity using Experimental Results from 
+    the Long-Term Ecological Research Network" held at NCEAS in September 1996.</title>
+    <creator id="clarence.lehman">
+        <individualName>
+            <salutation>Mr.</salutation>
+            <givenName>Clarence</givenName>
+            <surName>Lehman</surName>
+        </individualName>
+    </creator>
+    <annotation>
+        <propertyURI label="Subject">http://purl.org/dc/elements/1.1/subject</propertyURI>
+        <valueURI label="grassland biome">http://purl.obolibrary.org/obo/ENVO_01000177</valueURI>
+    </annotation>
+</dataset>  
+
+```
 
 ## /eml/annotations