[WebPubSub] Initial PR for web-pubsub-client (Azure#24029)

### Packages impacted by this PR
web-pubsub-client

### Issues associated with this PR


### Describe the problem that is addressed by this PR
This is the init PR for new package web-pubsub-client.

### What are the possible designs available to address the problem? If there are more than one possible design, why was the one in this PR chosen?


### Are there test cases added in this PR? _(If not, why?)_
Yes

### Provide a list of related PRs _(if any)_


### Command used to generate this PR:**_(Applicable only to SDK release request PRs)_

### Checklists
- [x] Added impacted package name to the issue description
- [ ] Does this PR needs any fixes in the SDK Generator?** _(If so, create an Issue in the [Autorest/typescript](https://github.com/Azure/autorest.typescript) repository and link it here)_
- [x] Added a changelog (if necessary)

.vscode/cspell.json

@@ -287,6 +287,10 @@
     {
       "filename": "sdk/loadtestservice/load-testing-rest/review/load-testing.api.md",
       "words": ["vusers"]
+    },
+    {
+      "filename": "sdk/web-pubsub/web-pubsub-client/review/web-pubsub-client.api.md",
+      "words": ["protobuf"]
     }
   ]
 }