Add summary stats report template

[ha0ye]

resolves #73:

• add a template script for a summary workflow
• add a template Rmarkdown report for the summary results
• add a function to create a MATSS research compendium that includes those template files and necessary package dependencies

[ha0ye]

To test:

1. Install MATSS from github:

remotes::install_github("weecology/MATSS")

2. Create a new R package compendium:

MATSS::create_MATSS_compendium(<path to new package to be created>)