Try to suggest typos

Ref af#45

lib/strictProxy.js

@@ -1,3 +1,14 @@
+const meant = require('meant')
+
+
+const didYouMean = (scmd, commands) => {
+    const bestSimilarity = meant(scmd, commands)
+
+    if (bestSimilarity.length > 0) {
+        throw new ReferenceError(`[envalid] Environment var ${scmd} not found, did you mean ${bestSimilarity.join(', ')}?`)
+    }
+}
+
 /**
 * Wrap the environment object with a Proxy that throws when:
 * a) trying to mutate an env var
@@ -19,6 +30,8 @@ module.exports = (envObj, originalEnv) => new Proxy(envObj, {
                 throw new ReferenceError(`[envalid] Environment accessed not found in envalid, but in the environment. Please add a validator for it: ${name}`)
             }
 
+            didYouMean(name, Object.keys(envObj))
+
             throw new ReferenceError(`[envalid] Environment var not found: ${name}`)
         }
 

package.json

@@ -38,7 +38,8 @@
   "license": "MIT",
   "dependencies": {
     "chalk": "2.1.0",
-    "dotenv": "4.0.0"
+    "dotenv": "4.0.0",
+    "meant": "1.0.0"
   },
   "typings": "envalid.d.ts"
 }

tests/test_strict.js

@@ -59,3 +59,10 @@ test('strict mode objects throw and suggest add validator if in orig env', () =>
     }, strictOption)
     assert.throws(() => env.FOO, '[envalid] Environment accessed not found in envalid, but in the environment. Please add a validator for it: FOO')
 })
+
+test('strict mode objects throw and suggest typo', () => {
+    const env = cleanEnv({}, {
+        BAR: str()
+    }, strictOption)
+    assert.throws(() => env.BAS, '[envalid] Environment var BAS not found, did you mean BAR?')
+})