[Feature request] Allow parsing of ISO-8601 datetime format in frontmatter

[kohane27]

Hello there! Thank you for creating such an awesome Obsidian plugin. It makes Quantified Self so much easier. However, I'm having the following issue.

I'm trying to track sleep, wake_up and the calculated sleep_hours. Example of frontmatter from daily note:

---
created: 2022-05-23
sleep: 2022-05-21T23:00:00+00:00
wake_up: 2022-05-22T07:00:00+00:00
sleep_hours: 8
---

Minimal example that doesn't work:

```tracker
searchType: frontmatter
searchTarget: wake_up
datasetName: Wake Up
line:
    title: "Sleep Habits"
    yAxisLabel: "Time (24h)"
```

I get the No valid Y value found in notes error. The reason for ISO-8601 date format is because I reply on = (this.wake_up - this.sleep).hours inline dataviewjs to calculate sleep_hours.

The following format with just the time works:

sleep: 23:00
wake_up: 07:00

But it means that my data won't comply with ISO-8601 (hence not very portable). Most importantly, without the date value, the calculated value is sometimes wrong.

I looked into the doc and the only mentioned of iso is ISO-8601 Date Format, but it's about setting the startDate and endDate in iso-8601.

Is it possible to add more input parameters, e.g., yAxisDateFormat and yAxisDisplayedFormat like the following:

```tracker
searchType: frontmatter
searchTarget: wake_up
datasetName: Wake Up
line:
    title: "Sleep Habits"
    yAxisLabel: "Time (24h)"
    yAxisDateFormat: iso-8601
    yAxisDisplayedFormat: "HH:mm:ss"
```

So that the Y-axis contains only the time but not the whole iso-8601?

Any help is much appreciated. Thank you again!