doc: add foot.1 man page

doc/meson.build

@@ -0,0 +1,18 @@
+scdoc = dependency('scdoc', native: true)
+scdoc_prog = find_program(scdoc.get_pkgconfig_variable('scdoc'), native: true)
+
+foreach man_src : ['foot.1.scd']
+  parts = man_src.split('.')
+  name = parts[-3]
+  section = parts[-2]
+  out = '@0@.@1@'.format(name, section)
+
+  custom_target(
+    out,
+    output: out,
+    input: man_src,
+    command: [sh, '-c', '@0@ < @INPUT@'.format(scdoc_prog.path())],
+    capture: true,
+    install: true,
+    install_dir: join_paths(get_option('mandir'), 'man@0@'.format(section)))
+endforeach