furrr for mltplx_exp.

[jeliason]

need to add for add_QuantileDist, update_intensity and update_dist as well

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.12 :tada:

Comparison is base (7f3dc11) 85.51% compared to head (aef3830) 85.63%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #63 +/- ## ========================================== + Coverage 85.51% 85.63% +0.12% ========================================== Files 32 32 Lines 842 877 +35 ========================================== + Hits 720 751 +31 - Misses 122 126 +4 ``` | [Impacted Files](https://codecov.io/gh/nateosher/DM-ME/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [R/MltplxExperiment.R](https://codecov.io/gh/nateosher/DM-ME/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Ui9NbHRwbHhFeHBlcmltZW50LlI=) | `93.10% <100.00%> (+0.87%)` | :arrow_up: | | [R/update\_dist.R](https://codecov.io/gh/nateosher/DM-ME/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Ui91cGRhdGVfZGlzdC5S) | `100.00% <100.00%> (ø)` | | | [R/update\_intensity.R](https://codecov.io/gh/nateosher/DM-ME/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Ui91cGRhdGVfaW50ZW5zaXR5LlI=) | `100.00% <100.00%> (ø)` | | ... and [4 files with indirect coverage changes](https://codecov.io/gh/nateosher/DM-ME/pull/63/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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[jeliason]

@nateosher @mariamasotti1 this adds parallelization functionality. To use more than 1 core locally, you can use plan(multisession(workers=2)) (or however many cores) after loading the future library and before creating a new MltplxExperiment. Also note that you will need to install DM-ME locally, rather than just loading with load_all(), as the multisession created will not recognize the loaded functions (if you want to use the parallelization during package development).

[mariamasotti1]

@jeliason yay!! should we add a short vignette for running in parallel?