[ACTION] Update Linear OAuth components

We should add an optional prop to the **Update Issue** and **Create Issue** actions for the Linear OAuth app (slug = `linear`):

From their docs: https://developers.linear.app/docs/oauth/oauth-actor-authorization
> To set the custom user name, set the createAsUser attribute with the user name and set displayIconUrl with the URL of the avatar in issueCreate or commentCreate mutations

We'll add the additional param to the authorization URL when these component changes are ready.

New optional prop:
- "Create As User" (default to `true`)
- If `Create As User` is `true`, set `createAsUser` to the user's `displayName` and `displayIconUrl` as `avatarUrl` (if not null). These can both be found by querying the `user` object (example below).
- If `Create As User` is `false`, then show 2 `additionalProps`:
1. Username (type string)
2. Display Icon URL (type string)

```
{
user(id: "me") {
displayName
avatarUrl
}
}
```