Additional Properties - typing is too loose for typescript

[zcstarr]

Additional properties and Patterned Properties append an any type to the end of the typing. The JSON schema spec doesn't quite line up with the typings generated. This would be a potentially breaking change for consuming clients. As they would all of a sudden generate types that didn't work with any. We want to move slowly here about introducing more specificity.

suggested change is probably

    if (s.additionalProperties ===  true || s.additionalProperties === undefined) {
      propertyTypings.push("  [k: string]: any;");
      }
    else if (s.additionalProperties !== false) {
      const subTypes: string[] = [];
      Object.values(s.additionalProperties!).forEach((prop: JSONSchema) => {
        const title = this.getSafeTitle(this.refToTitle(prop));
        if (subTypes.includes(title) === false) {
          subTypes.push(title);
        }
      });
      propertyTypings.push(`  [k: string]: ${subTypes.join(" | ")}`);
    } 

This issue will serve as tracking for open-rpc changes floating down the pipeline.