fix: add get method to type definitions of metric classes

[nflaig]

Current Limitation

At the moment there is no clean way to get a single metric value programmatically while using typescript.

The following is not possible as it causes type issues as the getters are implemented in javascript but are missing from type definitions.

const metric = register.getSingleMetric("process_cpu_user_seconds_total");

// Property 'get' does not exist on type 'Metric<string>'
const {value} = (await metric.get()).values[0]

Solution

Add get method to type definitions of each metric classes and define MetricObjectWithValues type which is returned by getters.

[nflaig]

@SimenB sorry for the ping but is there anything I can do to get this merged and released? 🙏

[SimenB]

Thanks!