core/ui: update logo (#5249)

* update logo

* use base64

* reference local file

* use svg, resize

* purple logo

* bigger

* move logo

README.md

@@ -1,4 +1,4 @@
-<a href="https://pomerium.com" title="Pomerium is a zero trust, context and identity aware access proxy."><img src="https://www.pomerium.com/wp-content/uploads/2021/08/Pomerium-H-white-bg.png" height="70" alt="pomerium logo"></a>
+<a href="https://pomerium.com" title="Pomerium is a zero trust, context and identity aware access proxy."><img src="./.github/logo.png" height="138" alt="pomerium logo"></a>
 
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