added some documentation and a watermark gauge

[Sanskar95]

No description provided.

[Max-Meldrum]

Suggested change

	//! - `allocator_metrics`
	//! - This enables recording metrics like total_bytes, bytes_remaining, allocation_counter
	//! - It is to be noted that without the prometheus_exporter flag the metrics will flow to stdout.
	//!
	//! - `state_metrics`
	//! - If this flag is enabled one can record state metrics like bytes_read, bytes_written which will be respective to the respective backend.
	//! - One can also record checkpoint related metrics like size of last checkpoint.
	//!
	//! - `allocator_metrics`
	//! - With this feature on, the runtime will record allocator metrics (e.g., total_bytes, bytes_remaining).
	//! - `state_metrics`
	//! - With this feature on, the runtime will record various state metrics (e.g., bytes in/out, checkpoint size).

[Max-Meldrum]

What is there now is a rustdoc comment for the first Enum variant. It needs to go on top.

Suggested change

	#[derive(Deserialize, Clone, Debug)]
	pub enum HardwareCounter {
	/// The type of hardware metric one wants to record.This is done while building the application and adding HardwareCounter
	/// enum options to it.
	/// An enum representing supported hardware counters
	///
	/// It is a wrapper around [Hardware] in order to support [Deserialize]
	#[derive(Deserialize, Clone, Debug)]
	pub enum HardwareCounter {

[Max-Meldrum]

Missing rustdoc for PerfEvents

/// Configurable hardware counters that may be added to an Operator's config
///
///```no_run
/// let mut perf_events = PerfEvents::new();
/// perf_events.add(HardwareCounter::CpuCycles);
/// perf_events.add(HardwareCounter::BranchMisses);
///```
#[derive(Deserialize, Clone, Debug, Default)]
pub struct PerfEvents {
    pub counters: Vec<HardwareCounter>,
}

[Max-Meldrum]

Good idea to include a simple application. We can however use an already defined operator.

operator: Arc::new(|| Map::new(|x| x + 10))

Also, please make sure it's indented properly.

[Max-Meldrum]

Suggested change

	/// An enum representing supported hardware counters with perf events as enum options
	///
	/// It is a wrapper around [Hardware] in order to support [Deserialize]
	///
	/// An enum representing supported hardware counters with perf events as enum options
	///
	/// It is a wrapper around [Hardware] in order to support [Deserialize]

[Max-Meldrum]

Closes #259