feat: add roman numeral filter for volume numbering

_includes/layouts/edition.njk

@@ -29,7 +29,7 @@ layout: base
 <hr class="rule">
 
 <div class="dateline">
-  <span class="vol">Volume {{ volume_number }}, Edition No. {{ edition_number }}</span>
+  <span class="vol">Volume {{ volume_number | roman }}, Edition No. {{ edition_number }}</span>
   <span class="place">Opelousas, Louisiana, {{ date | newsDate }}</span>
   <span class="price">Price 3 Acorns</span>
 </div>

eleventy.config.js

@@ -31,6 +31,19 @@ module.exports = function(eleventyConfig) {
         });
     });
 
+
+    eleventyConfig.addFilter("roman", function(num) {
+      const lookup = {M:1000,CM:900,D:500,CD:400,C:100,XC:90,L:50,XL:40,X:10,IX:9,V:5,IV:4,I:1};
+      let roman = '';
+      for (let i in lookup) {
+        while (num >= lookup[i]) {
+          roman += i;
+          num -= lookup[i];
+        }
+      } return roman; }
+    );
+
+  module.exports = function(eleventyConfig) {
     return {
         dir: {
             input: "content",