feat(initial): added portable mfem build system

include/meson_mfem_template/meson.build

@@ -0,0 +1,19 @@
+mfem_config = configuration_data()
+mfem_config.set_quoted('MESON_MFEM_TEMPLATE_VERSION', meson.project_version())
+mfem_config.set10('MESON_MFEM_USING_BUNDLED_MFEM', mfem_provider != 'system')
+
+mfem_config_header = configure_file(
+  input: 'config.hpp.in',
+  output: 'config.hpp',
+  configuration: mfem_config,
+  install: true,
+  install_tag: get_option('build_python') ? 'python-runtime' : 'devel',
+  install_dir: get_option('build_python')
+    ? python_build.get_install_dir() / 'meson_mfem_template' / 'include' / 'meson_mfem_template'
+    : get_option('includedir') / 'meson_mfem_template',
+)
+
+template_include_dep = declare_dependency(
+  include_directories: include_directories('..'),
+  sources: mfem_config_header,
+)