Add Brotli logo to README head (#535)

diff --git a/README.md b/README.md
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--- a/README.md
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@@ -1,3 +1,5 @@
+<p align="center"><img src="https://brotli.org/brotli.svg" alt="Brotli" width="64"></p>
+
 ### Introduction
 
 Brotli is a generic-purpose lossless compression algorithm that compresses data