refactor: do not install drivers as main dependency

Since, a user will never use all drivers together in a single app, we should ask
the end user to install them separately and not shipping it with this package

package.json

@@ -31,6 +31,8 @@
   "homepage": "https://github.com/poppinss/hash#readme",
   "devDependencies": {
     "@adonisjs/mrm-preset": "^2.0.3",
+    "@phc/argon2": "^1.0.9",
+    "@phc/bcrypt": "^1.0.2",
     "@types/node": "^12.6.2",
     "commitizen": "^3.1.1",
     "cz-conventional-changelog": "^2.1.0",
@@ -78,8 +80,6 @@
     "anyBranch": false
   },
   "dependencies": {
-    "@phc/argon2": "^1.0.9",
-    "@phc/bcrypt": "^1.0.2",
     "@poppinss/manager": "^1.1.2"
   }
 }

src/Drivers/Argon.ts

@@ -7,11 +7,11 @@
 * file that was distributed with this source code.
 */
 
-import * as argon2 from '@phc/argon2'
 import * as phc from '@phc/format'
-
 import { ArgonConfigContract, ArgonContract } from '../contracts'
 
+let argon2: any
+
 /**
  * Hash driver built on top of argon hashing algorithm. The driver adheres
  * to `phc` string format.
@@ -38,6 +38,9 @@ export class Argon implements ArgonContract {
   public version = 19
 
   constructor (private _config: ArgonConfigContract) {
+    if (!argon2) {
+      argon2 = require('@phc/argon2')
+    }
   }
 
   /**

src/Drivers/Bcrypt.ts

@@ -8,9 +8,10 @@
 */
 
 import { BcryptConfigContract, BcryptContract } from '../contracts'
-import * as bcrypt from '@phc/bcrypt'
 import * as phc from '@phc/format'
 
+let bcrypt: any
+
 /**
  * Generates and verifies hash using Bcrypt as underlying
  * algorigthm.
@@ -21,6 +22,9 @@ export class Bcrypt implements BcryptContract {
   public version = 98
 
   constructor (private _config: BcryptConfigContract) {
+    if (!bcrypt) {
+      bcrypt = require('@phc/bcrypt')
+    }
   }
 
   /**