Do not add / for html pages in rewriteDocLinks

Signed-off-by: Anastasia Rodionova <argali96@gmail.com>

.changeset/seven-wolves-clean.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs': patch
+---
+
+Do not add trailing slash for .html pages during doc links rewriting

plugins/techdocs/src/reader/transformers/rewriteDocLinks.test.ts

@@ -82,6 +82,7 @@ describe('normalizeUrl', () => {
     ['http://example.org/folder#intro', 'http://example.org/folder/#intro'],
     ['http://example.org/folder/#intro', 'http://example.org/folder/#intro'],
     ['http://example.org/folder#', 'http://example.org/folder/#'],
+    ['http://example.org/page.html', 'http://example.org/page.html'],
   ])('should handle %s', (url, expected) => {
     expect(normalizeUrl(url)).toEqual(expected);
   });

plugins/techdocs/src/reader/transformers/rewriteDocLinks.ts

@@ -58,7 +58,7 @@ export const rewriteDocLinks = (): Transformer => {
 export function normalizeUrl(input: string): string {
   const url = new URL(input);
 
-  if (!url.pathname.endsWith('/')) {
+  if (!url.pathname.endsWith('/') && !url.pathname.endsWith('.html')) {
     url.pathname += '/';
   }