Use lower-case arxiv as class name

For consistency.

src/replacements.ts

@@ -1,11 +1,11 @@
-import arXiv from './replacements/arXiv/index.js'
+import arxiv from './replacements/arxiv/index.js'
 import datetime from './replacements/datetime/index.js'
 import doi from './replacements/doi/index.js'
 import gcnCircular from './replacements/gcn-circular/index.js'
 import type { FindAndReplace } from './replacements/index.js'
 
 export const replacements: FindAndReplace[] = [
-  arXiv,
+  arxiv,
   datetime,
   doi,
   gcnCircular,

src/replacements/arXiv/index.ts → src/replacements/arxiv/index.ts

@@ -6,6 +6,6 @@ const articleId = /(?:\d{4}\.\d{5}|[a-z-]+\/\d{7})(?:v\d+)?/.source
 export default {
   find: new RegExp(`${marker}(${articleId})`, 'g'),
   replace(data, text, value) {
-    return data('arXiv', text, value)
+    return data('arxiv', text, value)
   },
 } satisfies FindAndReplace

src/replacements/arxiv/test.html

@@ -0,0 +1,4 @@
+<p>Old style arXiv reference: <data class="arxiv" value="astro-ph/1234567">arXiv:astro-ph/1234567</data></p>
+<p>New style arXiv reference: <data class="arxiv" value="1234.56789">arXiv:1234.56789</data></p>
+<p>URL references: <data class="arxiv" value="1234.56789">http://www.arxiv.org/abs/1234.56789</data>, <data class="arxiv" value="1234.56789">https://arxiv.org/abs/1234.56789</data></p>
+<p>Versioned arXiv reference: <data class="arxiv" value="1234.56789v2">arXiv:1234.56789v2</data></p>

src/replacements/arXiv/test.json → src/replacements/arxiv/test.json

@@ -12,7 +12,7 @@
           "type": "text",
           "value": "arXiv:astro-ph/1234567",
           "data": {
-            "class": "arXiv",
+            "class": "arxiv",
             "value": "astro-ph/1234567"
           }
         }
@@ -29,7 +29,7 @@
           "type": "text",
           "value": "arXiv:1234.56789",
           "data": {
-            "class": "arXiv",
+            "class": "arxiv",
             "value": "1234.56789"
           }
         }
@@ -46,7 +46,7 @@
           "type": "text",
           "value": "http://www.arxiv.org/abs/1234.56789",
           "data": {
-            "class": "arXiv",
+            "class": "arxiv",
             "value": "1234.56789"
           }
         },
@@ -58,7 +58,7 @@
           "type": "text",
           "value": "https://arxiv.org/abs/1234.56789",
           "data": {
-            "class": "arXiv",
+            "class": "arxiv",
             "value": "1234.56789"
           }
         }
@@ -75,7 +75,7 @@
           "type": "text",
           "value": "arXiv:1234.56789v2",
           "data": {
-            "class": "arXiv",
+            "class": "arxiv",
             "value": "1234.56789v2"
           }
         }