Adding ligature patch

https://st.suckless.org/patches/ligatures/
-> st-ligatures-alpha-scrollback-0.9

hb.h

@@ -0,0 +1,14 @@
+#include <X11/Xft/Xft.h>
+#include <hb.h>
+#include <hb-ft.h>
+
+typedef struct {
+  hb_buffer_t *buffer;
+  hb_glyph_info_t *glyphs;
+  hb_glyph_position_t *positions;
+  unsigned int count;
+} HbTransformData;
+
+void hbunloadfonts();
+void hbtransform(HbTransformData *, XftFont *, const Glyph *, int, int);
+void hbcleanup(HbTransformData *);