Simple version of get_template()
template()
a vector of the template names
template()#>#> [1] "classic" "copernicus" "crc" "demo" "demo_zh" #> [6] "docsens" "elsevier" "journal" "mail" "mdpi" #> [11] "mini" "nonpar" "nte_zh" "paper_zh" "pku_zh" #> [16] "poem" "rbasics" "thesis_zh" "ubt" "ucas_zh" #> [21] "calendar" "cchess" "chemistry" "chemistry_zh" "cumtb_zh" #> [26] "dnd" "guitar" "igo" "musix" "skak" #> [31] "uw" "zju_zh"