chore: expand techdocs.publisher.type with new types

Signed-off-by: djamaile <rdjamaile@gmail.com>

.changeset/cuddly-avocados-warn.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs-backend': patch
+---
+
+Expand techdocs.publisher.type with `googleGcs`,`awsS3`,`azureBlobStorage` and `openStackSwift`

plugins/techdocs-backend/config.d.ts

@@ -70,7 +70,12 @@ export interface Config {
      */
     publisher?:
       | {
-          type: 'local';
+          type:
+            | 'local'
+            | 'googleGcs'
+            | 'awsS3'
+            | 'azureBlobStorage'
+            | 'openStackSwift';
 
           local?: {
             /**