Add webmention styles and share buttons

- Created a new SCSS file for webmention styles to enhance the appearance of comments and reactions.
- Added HTML partial for share buttons including Twitter, Facebook, LinkedIn, Reddit, and WhatsApp.
- Updated the main SCSS file to include webmention styles and removed the old CSS file for webmentions.
- Updated asset integrity for the compiled CSS file.

assets/sass/root.scss

@@ -0,0 +1,29 @@
+:root {
+	--blockquote-border-size: 4px;
+	--blockquote-background-color: rgb(248 248 248);
+
+	--heading-border-size: 4px;
+
+	--link-background-color: 189, 195, 199;
+	--link-background-opacity: 0.5;
+	--link-background-opacity-hover: 0.7;
+
+	--pre-background-color: #272822;
+	--pre-text-color: #f8f8f2;
+
+	--code-background-color: rgba(0, 0, 0, 0.12);
+	--code-text-color: #808080;
+
+	--table-border-color: #dadada;
+	--tr-even-background-color: #efefee;
+
+	@media (prefers-color-scheme: dark) {
+		--code-background-color: #272822;
+		--code-text-color: rgba(255, 255, 255, 0.9);
+
+		--table-border-color: #717171;
+		--tr-even-background-color: #545454;
+
+		--blockquote-background-color: rgb(75 75 75);
+	}
+}