Minor rST formatting
Minor clarification to not pointing directly to formulas repos
Updated Formula Best Practices doc with several recommendations
Change all state examples to use short-dec format for consistency

Closes #12419.

The command used to search the docs for state examples is below. This
generates a file in Vim's quickfix format that can be loaded with the -q
flag.

find . -type f \( -name '*.rst' -o -name '*.py' \) -print0
    | xargs -0 -P10 -n1 awk '
        BEGIN { RS=""; FS="\n" }
        { linenr = linect; linect += (NF + 1) }
        /^\s+[a-zA-Z0-9'\''_-]+:\n\s+[a-zA-Z0-9'\''_-]+:\n\s+- / {
            print FILENAME "|" linenr + 2 "|", $1
        }
    ' > ./salt-states.quickfix
Merge pull request #18971 from whiteinge/doc-formula-style-guide

Fixes and additions to the Formula best practices doc