feat(corp/rih): add macro to render Markdown->yew::Html statically

This makes it possible to embed long texts from Markdown files instead
of dealing with writing the weird HTML-tags inside the yew macros,
which will be much easier for content editors to deal with.

Change-Id: Idc4e67404fcfe2b8d5083cf556df1c701ba17660
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8648
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

corp/rih/static-markdown/src/lib.rs

@@ -0,0 +1,27 @@
+extern crate proc_macro;
+
+use comrak::{markdown_to_html, ComrakOptions};
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, LitStr};
+
+#[proc_macro]
+pub fn markdown(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as LitStr);
+
+    let mut options = ComrakOptions::default();
+    options.extension.strikethrough = true;
+    options.extension.tagfilter = true;
+    options.extension.table = true;
+    options.extension.autolink = true;
+
+    let rendered_html = markdown_to_html(&input.value(), &options);
+
+    let tokens = quote! {
+        yew::virtual_dom::VNode::VRaw(yew::virtual_dom::VRaw {
+            html: #rendered_html.into(),
+        })
+    };
+
+    tokens.into()
+}