Standardize Package

[maotian06]

Description

Add the License section to README.md and add the license file based on @tyamaguchi-ucla 's suggestion.

Checklist

• [x] This PR does NOT contain Protected Health Information (PHI). A repo may need to be deleted if such data is uploaded.
  Disclosing PHI is a major problem[^1] - Even a small leak can be costly[^2].

• [x] This PR does NOT contain germline genetic data[^3], RNA-Seq, DNA methylation, microbiome or other molecular data[^4].

[^1]: UCLA Health reaches $7.5m settlement over 2015 breach of 4.5m patient records [^2]: The average healthcare data breach costs $2.2 million, despite the majority of breaches releasing fewer than 500 records. [^3]: Genetic information is considered PHI. Forensic assays can identify patients with as few as 21 SNPs [^4]: RNA-Seq, DNA methylation, microbiome, or other molecular data can be used to predict genotypes (PHI) and reveal a patient's identity.

• [x] This PR does NOT contain other non-plain text files, such as: compressed files, images (e.g. .png, .jpeg), .pdf, .RData, .xlsx, .doc, .ppt, or other output files.

  To automatically exclude such files using a .gitignore file, see here for example.

• [x] I have read the code review guidelines and the code review best practice on GitHub check-list.

• [x] I have set up or verified the main branch protection rule following the github standards before opening this pull request.

• [x] The name of the branch is meaningful and well formatted following the standards, using [AD_username (or 5 letters of AD if AD is too long)]-[brief_description_of_branch].

• [ ] I have added the major changes included in this pull request to the CHANGELOG.md under the next release version or unreleased, and updated the date.

[tyamaguchi-ucla]

@maotian06 Also, I think we should create a release with the current main before merging the existing PRs.

[dan-knight]

The Maintainer field is usually Paul. Let's confirm with @pboutros that we should change it to him.

I'd use the @AuthorsR format for the authors (see CEV's DESCRIPTION file). I'd recommend Paul to have the cre role as maintainer, Natalie to have aut, and you to have ctb. (See this resource on the author roles.)

[dan-knight]

I'll update this to NEWS.md format before we merge.

EDIT: Done

[maotian06]

@dan-knight @tyamaguchi-ucla I have implemented all the updates. Can you help me take a look?