Refactor the `default` variable to accept a list, enabling the
specification of multiple default IDEs. This change allows users
to manage configurations for multiple IDEs more efficiently.
- Updated `default` type from string to list(string)
- Iterated over default IDEs to generate corresponding resources
- Ensured backward compatibility where single IDE configs were used
Due to the highest priority of the `ide_download_link` parameter in the `(jetbrains-gateway://...` within IDEA, the pre-configured download address will be overridden when using [IDEA's offline mode](https://www.jetbrains.com/help/idea/fully-offline-mode.html). Therefore, it is necessary to configure the `download_base_link` parameter for the `jetbrains_gateway` module to change the value of `ide_download_link`.
Due to the highest priority of the `ide_download_link` parameter in the `(jetbrains-gateway://...` within IDEA, the pre-configured download address will be overridden when using [IDEA's offline mode](https://www.jetbrains.com/help/idea/fully-offline-mode.html). Therefore, it is necessary to configure the `download_base_link` parameter for the `jetbrains_gateway` module to change the value of `ide_download_link`.