Fix @types/lru-cache missing in dependency

[boydc2014]

Fixes #1369

Description

Add lru-cache as dependency since it's been exposed in expression library.

Otherwise we will hit

node_modules/botframework-expressions/lib/commonRegex.d.ts:9:27 - error TS7016: Could not find a declaration file for module 'lru-cache'. 
'C:/Users/donglei/code/testg/node_modules/lru-cache/index.js' implicitly has an 'any' type.
  Try `npm install @types/lru-cache` if it exists or add a new declaration (.d.ts) file containing `declare module 'lru-cache';`

9 import * as LRUCache from 'lru-cache';
                            ~~~~~~~~~~~