Replace SVG images with PNG alternatives in README

Updated image sources in README for better visibility.

Author: muhammadsammy

README.md

@@ -1,8 +1,8 @@
-<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/ci/muhammadsammy/free-vscode-csharp.svg?variant=outline&size=sm&mode=dark"><img alt="CI" src="https://www.shieldcn.dev/github/ci/muhammadsammy/free-vscode-csharp.svg?variant=outline&size=sm&mode=light"></picture>
-<picture><source media="(prefers-color-scheme: dark)" src="https://www.shieldcn.dev/openvsx/downloads/muhammad-sammy/csharp.svg?variant=branded&size=sm&mode=dark"><img alt="Downloads" src="https://www.shieldcn.dev/openvsx/downloads/muhammad-sammy/csharp.svg?variant=branded&size=sm&mode=light"></picture>
-<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/release/muhammadsammy/free-vscode-csharp.svg?size=sm&mode=dark&variant=outline"><img alt="Release" src="https://www.shieldcn.dev/github/release/muhammadsammy/free-vscode-csharp.svg?size=sm&mode=light&variant=outline"></picture>
-<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/open-issues/muhammadsammy/free-vscode-csharp.svg?variant=outline&size=sm&mode=dark"><img alt="Open issues" src="https://www.shieldcn.dev/github/open-issues/muhammadsammy/free-vscode-csharp.svg?variant=outline&size=sm&mode=light"></picture>
-<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/open-prs/muhammadsammy/free-vscode-csharp.svg?variant=outline&size=sm&mode=dark"><img alt="Open PRs" src="https://www.shieldcn.dev/github/open-prs/muhammadsammy/free-vscode-csharp.svg?variant=outline&size=sm&mode=light"></picture>
+<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/ci/muhammadsammy/free-vscode-csharp.png?variant=outline&size=sm&mode=dark"><img alt="CI" src="https://www.shieldcn.dev/github/ci/muhammadsammy/free-vscode-csharp.png?variant=outline&size=sm&mode=light"></picture>
+<picture><source media="(prefers-color-scheme: dark)" src="https://www.shieldcn.dev/openvsx/downloads/muhammad-sammy/csharp.png?variant=branded&size=sm&mode=dark"><img alt="Downloads" src="https://www.shieldcn.dev/openvsx/downloads/muhammad-sammy/csharp.png?variant=branded&size=sm&mode=light"></picture>
+<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/release/muhammadsammy/free-vscode-csharp.png?size=sm&mode=dark&variant=outline"><img alt="Release" src="https://www.shieldcn.dev/github/release/muhammadsammy/free-vscode-csharp.png?size=sm&mode=light&variant=outline"></picture>
+<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/open-issues/muhammadsammy/free-vscode-csharp.png?variant=outline&size=sm&mode=dark"><img alt="Open issues" src="https://www.shieldcn.dev/github/open-issues/muhammadsammy/free-vscode-csharp.png?variant=outline&size=sm&mode=light"></picture>
+<picture><source media="(prefers-color-scheme: dark)" srcset="https://www.shieldcn.dev/github/open-prs/muhammadsammy/free-vscode-csharp.png?variant=outline&size=sm&mode=dark"><img alt="Open PRs" src="https://www.shieldcn.dev/github/open-prs/muhammadsammy/free-vscode-csharp.png?variant=outline&size=sm&mode=light"></picture>
 
 # free-csharp-vscode