Clean up make check: R6 method docs and R CMD check NOTEs - #13

Process completed with exit code 31.

file=inst/app/app.R,line=451,col=7,[object_usage_linter] no visible global function definition for 'icon'

file=inst/app/app.R,line=438,col=5,[object_usage_linter] no visible binding for global variable 'tags'

file=inst/app/app.R,line=430,col=16,[assignment_linter] Replace <<- by assigning to a specific environment (with assign() or <-) to avoid hard-to-predict behavior.

file=inst/app/app.R,line=424,col=5,[object_usage_linter] no visible global function definition for 'invalidateLater'

file=inst/app/app.R,line=423,col=29,[object_usage_linter] no visible global function definition for 'renderUI'

file=inst/app/app.R,line=420,col=1,[cyclocomp_linter] Reduce the cyclomatic complexity of this expression from 49 to at most 15. Consider replacing high-complexity sections like loops and branches with helper functions.

file=inst/app/app.R,line=400,col=121,[line_length_linter] Lines should not be more than 120 characters. This line is 127 characters.

file=inst/app/app.R,line=192,col=121,[line_length_linter] Lines should not be more than 120 characters. This line is 173 characters.

file=inst/app/app.R,line=3,col=121,[line_length_linter] Lines should not be more than 120 characters. This line is 197 characters.

file=inst/app/app.R,line=1,col=4,[commented_code_linter] Remove commented code.