Add region capture option

meson.build

@@ -33,6 +33,7 @@ src = [
     'src/gui/Subsection.cpp',
     'src/Utils.cpp',
     'src/WindowUtils.cpp',
+    'src/RegionSelector.cpp',
     'src/Config.cpp',
     'src/GsrInfo.cpp',
     'src/Process.cpp',
@@ -65,6 +66,7 @@ executable(
         dependency('threads'),
         dependency('xcomposite'),
         dependency('xfixes'),
+        dependency('xext'),
         dependency('xi'),
         dependency('xcursor'),
         dependency('libpulse-simple'),