Add text ability for create.histogram

[stefaneng]

Description

Implement add.text capabilities for create.histogram. Identical implementation to create.barplot

Closes #21

Checklist

• This PR does NOT contain PHI or germline genetic data. A repo may need to be deleted if such data is uploaded. Disclosing PHI is a major problem.
• This PR does NOT contain molecular files, compressed files, output files such as images (e.g. .png, .jpeg), .pdf, .RData, .xlsx, .doc, .ppt, or other non-plain-text files. To automatically exclude such files using a .gitignore file, see here for example.
• I have read the code review guidelines and the code review best practice on GitHub check-list.
• I have set up or verified the main branch protection rule following the github standards before opening this pull request.
• 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.

Example

suppressPackageStartupMessages(library(BoutrosLab.plotting.general));
set.seed(10);
x <- rnorm(100);
create.histogram(
    x = x,
    add.text = TRUE,
    text.x = -2,
    text.y = 20,
    text.labels = 'Text'
    );

^{Created on 2023-01-09 with reprex v2.0.2}

[tyamaguchi-ucla]

Looks good to me. @dan-knight for final approval.

[lydiayliu]

Looks good! Thanks @stefaneng