tree-sitter: vendor tree-sitter runtime

tree-sitter/tree-sitter commit 7685b7861ca475664b6ef57e14d1da9acf741275

Included files are:
lib/include/tree-sitter/*.h
lib/src/*.[ch]
LICENSE

src/tree_sitter/lib.c

@@ -0,0 +1,20 @@
+// The Tree-sitter library can be built by compiling this one source file.
+//
+// The following directories must be added to the include path:
+//   - include
+//   - utf8proc
+
+#define _POSIX_C_SOURCE 200112L
+#define UTF8PROC_STATIC
+
+#include "./get_changed_ranges.c"
+#include "./language.c"
+#include "./lexer.c"
+#include "./node.c"
+#include "./parser.c"
+#include "./stack.c"
+#include "./subtree.c"
+#include "./tree_cursor.c"
+#include "./tree.c"
+#include "./utf16.c"
+#include "utf8proc.c"