Finish refactoring src/**/*.js to use import & export

src/encoding/armor.js

@@ -402,7 +402,7 @@ function armor(messagetype, body, partindex, parttotal) {
   return result.join('');
 }
 
-module.exports = {
+export default {
   encode: armor,
   decode: dearmor
 };

src/encoding/base64.js

@@ -108,7 +108,7 @@ function r2s(t) {
   return new Uint8Array(r);
 }
 
-module.exports = {
+export default {
   encode: s2r,
   decode: r2s
 };