fix: use absolute GitHub URL for cover image in README files (#1208)

Author: enesgules

README.md

@@ -1,4 +1,4 @@
-![Cover](public/cover.png)
+![Cover](https://github.com/upstash/context7/blob/master/public/cover.png?raw=true)
 
 [![Install MCP Server](https://cursor.com/deeplink/mcp-install-dark.svg)](https://cursor.com/en/install-mcp?name=context7&config=eyJ1cmwiOiJodHRwczovL21jcC5jb250ZXh0Ny5jb20vbWNwIn0%3D) [<img alt="Install in VS Code (npx)" src="https://img.shields.io/badge/Install%20in%20VS%20Code-0098FF?style=for-the-badge&logo=visualstudiocode&logoColor=white">](https://insiders.vscode.dev/redirect?url=vscode%3Amcp%2Finstall%3F%7B%22name%22%3A%22context7%22%2C%22command%22%3A%22npx%22%2C%22args%22%3A%5B%22-y%22%2C%22%40upstash%2Fcontext7-mcp%40latest%22%5D%7D)
 

i18n/README.zh-CN.md

@@ -1,4 +1,4 @@
-![Cover](../public/cover.png)
+![Cover](https://github.com/upstash/context7/blob/master/public/cover.png?raw=true)
 
 # Context7 MCP - 为所有 Prompt 获取最新文档
 

packages/mcp/README.md

@@ -1,4 +1,4 @@
-![Cover](public/cover.png)
+![Cover](https://github.com/upstash/context7/blob/master/public/cover.png?raw=true)
 
 [![Install MCP Server](https://cursor.com/deeplink/mcp-install-dark.svg)](https://cursor.com/en/install-mcp?name=context7&config=eyJ1cmwiOiJodHRwczovL21jcC5jb250ZXh0Ny5jb20vbWNwIn0%3D) [<img alt="Install in VS Code (npx)" src="https://img.shields.io/badge/Install%20in%20VS%20Code-0098FF?style=for-the-badge&logo=visualstudiocode&logoColor=white">](https://insiders.vscode.dev/redirect?url=vscode%3Amcp%2Finstall%3F%7B%22name%22%3A%22context7%22%2C%22command%22%3A%22npx%22%2C%22args%22%3A%5B%22-y%22%2C%22%40upstash%2Fcontext7-mcp%40latest%22%5D%7D)