Add two new time filters to jinja

[DavidHuber-NOAA]

Description This adds the timetools functions to_timedelta and add_to_datetime to the jinja filter list.

Here's an example of how to use the new filters:

{% for restart_offset in ["+3", "+6", "+9"] %}
{% set restart_delta = restart_offset | to_timedelta %}
{% set restart_datetime = current_cycle | add_to_datetime(restart_delta) %}
{% endfor %}

Needed for https://github.com/NOAA-EMC/global-workflow/pull/2491

Type of change

• [x] New feature (non-breaking change which adds functionality)
• [x] This change requires a documentation update

How Has This Been Tested?

• [x] pynorms
• [x] pytests

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] My changes need updates to the documentation. I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] New and existing tests pass with my changes

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 47.84%. Comparing base (c237f19) to head (cdc9751).

Files	Patch %	Lines
src/wxflow/jinja.py	33.33%	0 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #25 +/- ## =========================================== - Coverage 47.90% 47.84% -0.06% =========================================== Files 18 18 Lines 1647 1649 +2 Branches 333 335 +2 =========================================== Hits 789 789 Misses 801 801 - Partials 57 59 +2 ```

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[DavidHuber-NOAA]

Sure thing. Done.