add blob content contribute role to backend (Azure-Samples#206)

## Purpose
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does it solve or functionality does it add? -->
* ...

## Does this introduce a breaking change?
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[ ] Yes
[ ] No
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## Pull Request Type
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[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:
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## How to Test
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git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install
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* Test the code
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## What to Check
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## Other Information
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Author: LittleLittleCloud

infra/main.bicep

@@ -466,6 +466,16 @@ module storageRoleBackend 'core/security/role.bicep' = {
   }
 }
 
+module storageContribRoleBackend 'core/security/role.bicep' = {
+  scope: storageResourceGroup
+  name: 'storage-contribrole-backend'
+  params: {
+    principalId: web.outputs.SERVICE_WEB_IDENTITY_PRINCIPAL_ID
+    roleDefinitionId: 'ba92f5b4-2d11-453d-a403-e96b0029c9fe'
+    principalType: 'ServicePrincipal'
+  }
+}
+
 module searchRoleBackend 'core/security/role.bicep' = {
   scope: searchServiceResourceGroup
   name: 'search-role-backend'