Add better support for markdown (switch nano-markdown for markdown-it as the former doesn't support backtick-code-formatting), add Markdown element. See #1929

src/UI/Base/Markdown.svelte

@@ -0,0 +1,17 @@
+<script lang="ts">
+  import markdownit from "markdown-it"
+  import { UIEventSource } from "../../Logic/UIEventSource"
+  const md = markdownit()
+  export let src: string
+  export let srcWritable: UIEventSource<string> = undefined
+  srcWritable?.addCallbackAndRunD(t => {
+    src = t
+  })
+  if(typeof src !== "string") {
+    throw "Markdown.svelte got a non-string object"
+  }
+</script>
+{#if src?.length > 0}
+  {@html md.render(src)}
+{/if}
+