Returns the template mode to be applied to templates resolved by
this template resolver.
If template mode patterns (see
#setXhtmlTemplateModePatterns(Set),
#setHtml5TemplateModePatterns(Set), etc.) are also set, they have higher
priority than the template mode set here (this would act as a default).
Note that this template mode also may not be applied if the template resource name
ends in a known file name suffix:
.html,
.htm,
.xhtml,
.xml,
.js,
.json,
.css,
.rss,
.atom,
.txt. If this behaviour needs to be overridden so
that template name is always applied, the
#setForceTemplateMode(boolean) will need to be set.