Fix relative path of images (#14)

Merge change as @msporny mentioned this is just editorial change and with very limited changes involving only references to the 3 images.

Author: HJunyuan

index.html

@@ -471,15 +471,15 @@ <h4>OpenAttestationEmbeddedRenderer</h4>
       <figure id="oa-embedded-certificate">
         <img
           style="width: 100%"
-          src="/images/oa-embedded-certificate.png"
+          src="images/oa-embedded-certificate.png"
           alt="Certificate Template"
         />
         <figcaption>Certificate Template</figcaption>
       </figure>
       <figure id="oa-embedded-transcript">
         <img
           style="width: 100%"
-          src="/images/oa-embedded-transcript.png"
+          src="images/oa-embedded-transcript.png"
           alt="Transcript Template"
         />
         <figcaption>Transcript Template</figcaption>
@@ -524,7 +524,7 @@ <h5>Action API</h5>
             <figure id="oa-embedded-sequence-diagram">
                 <img
                         style="width: 100%"
-                        src="/images/oa-embedded-sequence-diagram.png"
+                        src="images/oa-embedded-sequence-diagram.png"
                         alt="Sequence Diagram"
                 />
                 <figcaption>Sequence Diagram</figcaption>