add: アラート記法に対応

src/lib/components/Markdown.css

@@ -194,4 +194,51 @@
         margin: 1rem;
         font-size: 1.5rem;
     }
+    & .markdown-alert {
+        padding: 8px 16px;
+        margin: 1em 0;
+
+        & .markdown-alert-title {
+            display: flex;
+            align-items: center;
+            & svg {
+                fill: currentColor;
+                margin-right: 8px;
+            }
+        }
+        & p {
+            margin: 0;
+        }
+
+        &.markdown-alert-note {
+            border-left: solid #0969da 4px;
+            & .markdown-alert-title {
+                color: #0969da;
+            }
+        }
+        &.markdown-alert-tip {
+            border-left: solid #1a7f37 4px;
+            & .markdown-alert-title {
+                color: #1a7f37;
+            }
+        }
+        &.markdown-alert-important {
+            border-left: solid #8250df 4px;
+            & .markdown-alert-title {
+                color: #8250df;
+            }
+        }
+        &.markdown-alert-warning {
+            border-left: solid #9a6700 4px;
+            & .markdown-alert-title {
+                color: #9a6700;
+            }
+        }
+        &.markdown-alert-caution {
+            border-left: solid #cf222e 4px;
+            & .markdown-alert-title {
+                color: #cf222e;
+            }
+        }
+    }
 }

src/lib/components/Markdown.ts

@@ -9,6 +9,7 @@ import rehypeslug from 'rehype-slug'
 import rehypeKatex from 'rehype-katex'
 import rehypeHighlight from 'rehype-highlight'
 import rehypeExternalLinks from 'rehype-external-links'
+import rehypeGithubAlert from 'rehype-github-alert'
 import rehypeStringify from 'rehype-stringify'
 
 
@@ -22,6 +23,7 @@ function Perser(mdtext: string): string {
         .use(rehypeKatex, {output:'mathml'})    // 数式
         .use(rehypeHighlight)   // Syntax highlight
         .use(rehypeExternalLinks, {target:'_blank', rel:['noreferrer','noopener']}) // 外部サイトを新規タブで開く
+        .use(rehypeGithubAlert)
         .use(rehypeStringify, {allowDangerousHtml: true})
         .processSync(mdtext)
         .toString()