vlib,tools: add an arrays.diff module, implement a simple platform independent tool v diff file1.txt file2.txt using it (#24428)

examples/diff.v

@@ -0,0 +1,41 @@
+module main
+
+import arrays.diff
+import os
+
+// diff_files generate diff for two files.
+fn diff_files(src_file string, dst_file string) !string {
+	src := os.read_lines(src_file)!
+	dst := os.read_lines(dst_file)!
+
+	mut ctx := diff.diff(src, dst)
+	return ctx.generate_patch(colorful: true, block_header: true)
+}
+
+fn main() {
+	f1 := "Module{
+	name: 'Foo'
+	description: 'Awesome V module.'
+	version: '0.0.0'
+	dependencies: []
+}
+"
+	f2 := "Module{
+	name: 'foo'
+	description: 'Awesome V module.'
+	version: '0.1.0'
+	license: 'MIT'
+	dependencies: []
+}
+"
+	p1 := 'diff_f1.txt'
+	p2 := 'diff_f2.txt'
+	os.write_file(p1, f1)!
+	os.write_file(p2, f2)!
+
+	str := diff_files(p1, p2)!
+	println(str)
+
+	os.rm(p1)!
+	os.rm(p2)!
+}