Adding docs for new model support of GPT-5 Pro

Author: bsyedumar

docs/account-management/billing-management.mdx

@@ -49,6 +49,7 @@ This section covers unit pricing. For plan quotas and features, see [Compare Pla
 | Model         | Input Price (per 1M tokens) | Cached Input Price (per 1M tokens) | Output Price (per 1M tokens) | Max Context Size | Search Price (per 1k calls) | Image Support |
 |---------------|-----------------------------|-------------------------------------|------------------------------|------------------|-----------------------------|---------------|
 | GPT-5         | $1.30                        | $0.13                               | $10.00                       | 400k tokens      | $10.00                      | Text only (token-based) |
+| GPT-5 pro     | $10.00                      | N/A                                 | $15.00                       | 400k tokens      | $120.00                     |  Text only (token-based) |
 | GPT-5 mini    | $0.30                        | $0.03                               | $2.00                        | 400k tokens      | $10.00                      | Text only (token-based) |
 | GPT-5 nano    | $0.10                        | $0.01                               | $0.40                         | 400k tokens      | N/A                         | Text only (token-based) |
 | GPT-5 Chat    | $1.30                        | $0.13                               | $10.00                       | 400k tokens      | N/A                         | Text only (token-based) |