You can use handlebar syntax on your issue or pull request body (better yet, create a template with relevant things), this app will compile the handlebar template and update body of pull request.

One of the usecase can be adding a link to build or deployment url for that particular PR, normally github doesn't allow variables, but with this, you'd be able to add a link with {{id}} and it'll replace it with issue/pr id.

Once a PR or Issue is created or edited, it's ran through handlebars with some variables the interface for which is given below:

export interface ITemplateVars {
    id: number;
    user: {
        login: string;
        id: number;
        avatar_url: string;
        url: string;
    };
    issueData?: { // as of now there's no issue data, if required please open an issue
    };
    pullData?: {
        html_url: string;
        diff_url: string;
        patch_url: string;
        issue_url: string;
        branch: string;
    };
    labels: WebhookPayloadIssuesIssueLabelsItem[];
}

The issue's body is then updated to have this resulting new body