Add a gallery example showing different front styles (#1022)
Add a gallery example showing different front styles (#1022)

* Add a gallery example showing different line front styles

Co-authored-by: Dongdong Tian <3eae6d0b95aef6af8a0d785fe9f127268703c43c@gmail.com>
Co-authored-by: Yao Jiayuan <4a3b81659a3e41c1b1e422525b254e800e0ba11d@gmail.com>
Co-authored-by: Will Schlitzer <cfa40c04a9aa95e6d82d1f70a59f101092295f6a@gmail.com>
GenericMappingTools/gmt-python,GenericMappingTools/gmt-python