Update .delete() request options interface to include body

[danipavic]

Library's .delete() function takes RequestOptions as the first parameter, however, the interface is missing the body property which you are able to include when making a delete request via Angular HTTP client. The request options interface should be updated to support body.

Current library interface:

export declare type RequestOptions = {
    headers?: HttpHeaders | PlainHeaders;
    observe?: any;
    params?: HttpParams | {
        [param: string]: string | string[];
    } | object;
    routeParams?: {
        [param: string]: string | string[];
    };
    reportProgress?: boolean;
    responseType?: any;
    withCredentials?: boolean;
};

Angular's interface:

{
    headers?: HttpHeaders | {
        [header: string]: string | string[];
    };
    observe: 'response';
    context?: HttpContext;
    params?: HttpParams | {
        [param: string]: string | number | boolean | ReadonlyArray<string | number | boolean>;
    };
    reportProgress?: boolean;
    responseType?: 'json';
    withCredentials?: boolean;
    body?: any | null;
}