chore: address warnings and notes from R CMD check

[kellijohnson-NOAA]

While looking at the output from R CMD check I saw a few warnings and notes

• Add .octocov.yml to .Rbuildignore
• Add .devcontainer to Rbuildignore
• Change \code{\link[asar:create_figures_doc]{asar::create_figures_doc()}} to an html link because {asar} is not included as an import therefore a note is being generated about this documentation, i.e., not everyone will be able to build the documentation
• {kableExtra} is in the tests but not in any of the functions so a warning is produced about it being imported, should it be used in the code somewhere?
• README.md is not allowed in data folder
• na.omit() needs to be stats::na.omit()
• calc_kqs: no visible global function definition for 'na.omit'
• convert_output: no visible binding for global variable 'month'
• theme_table() has missing braces or markup in the documentation