Add meta tags for slack/discord preview

src/main/kotlin/moe/kageru/kodeshare/pages/AboutPage.kt

@@ -11,6 +11,9 @@ object AboutPage {
     val content = HtmlContent(HttpStatusCode.OK) {
         head {
             link(rel = "stylesheet", href = "/style.css", type = "text/css")
+            meta(content = "About Kodeshare – a FOSS [ph]astebin alternative") {
+                attributes["property"] = "og:title"
+            }
         }
         body {
             div("wrapper") {

src/main/kotlin/moe/kageru/kodeshare/pages/Homepage.kt

@@ -8,7 +8,7 @@ object Homepage {
     val content = HtmlContent(HttpStatusCode.OK) {
         head {
             link(rel = "stylesheet", href = "/style.css", type = "text/css")
-            meta(content = "Kodeshare – a FOSS pastebin alternative") {
+            meta(content = "Kodeshare – a FOSS [ph]astebin alternative") {
                 attributes["property"] = "og:title"
             }
         }

src/main/kotlin/moe/kageru/kodeshare/pages/PastePage.kt

@@ -13,6 +13,13 @@ object PastePage {
                 type = "text/css"
             )
             script(src = "https://p.kageru.moe/static/hl.js") {}
+            meta(content = "Kodeshare – a FOSS [ph]astebin alternative") {
+                attributes["property"] = "og:title"
+            }
+            // Show the first 3 lines in preview/embed for applications like discord, slack, or skype
+            meta(content = content.lines().take(3).joinToString("\n")) {
+                attributes["property"] = "og:description"
+            }
             unsafe {
                 +"<script>hljs.initHighlightingOnLoad();</script>"
                 +"<style>html{scrollbar-color: transparent transparent;}::-webkit-scrollbar{display: none;}</style>"