update button asset to use github repo

Author: nullfunc

README.md

@@ -1,6 +1,6 @@
 # Nextra
 
-[![1-click-deploy](https://defang.io/deploy-with-defang.svg)](https://portal.defang.dev/redirect?url=https%3A%2F%2Fgithub.com%2Fnew%3Ftemplate_name%3Dsample-nextjs-documentation-template%26template_owner%3DDefangSamples)
+[![1-click-deploy](https://raw.githubusercontent.com/DefangLabs/defang-assets/main/Logos/Buttons/SVG/deploy-with-defang.svg)](https://portal.defang.dev/redirect?url=https%3A%2F%2Fgithub.com%2Fnew%3Ftemplate_name%3Dsample-nextjs-documentation-template%26template_owner%3DDefangSamples)
 
 This template is a documentation starter project developed using Nextra, designed to streamline the creation of your documentation and quickly build a digital knowledgebase. You can add content easily by simply adding markdown files. This code-free solution requires no adjustments to the basic structure. We have prepared all the essential files for deployment. By spending just a few minutes setting up the environment, as detailed in the prerequisites, and executing the commands in our step-by-step guide, your website will be ready to go live in no time!