add crypto outside pages

crypto.js

@@ -0,0 +1,19 @@
+const chars = "abcdefghijklmnopqrstuvwxyz";
+
+export const stoi = {};
+export const itos = {};
+for (let i = 0; i < chars.length; i++) {
+  const ch = chars[i];
+  stoi[ch] = i;
+  itos[i] = ch;
+}
+export function ceaser_cipher(string, n = 0){
+  string = string.replace(/[^a-zA-Z]/g, '').toLowerCase();
+  let result = "";
+  for (let i = 0; i < string.length; i++) {
+    let c = string[i];
+    result +=  itos[(stoi[c] + n) % 26]
+  }
+  return result;
+}
+