Fix issue that causes routes grouped with prefix to generate 404.

[AbdullahFaqeir]

##Issue Reference
#50

##Description
When multilingual route(s) is/are defined in a prefixed group, the routes generates 404 pages.

How To Test This?

<?php

use Illuminate\Support\Facades\Route;

Route::get('/', function () {
    return view('welcome');
});

Route::group(['prefix' => 'blog'], function () {
    $c = App\Http\Controllers\BlogController::class;

    Route::multilingual('/', [$c, 'index'])->name('blog.index');
    Route::multilingual('/create', [$c, 'create'])->name('blog.create');
    Route::multilingual('/edit/{post}', [$c, 'edit'])->name('blog.edit');
    Route::multilingual('/show/{post}', [$c, 'show'])->name('blog.show');
});

Then navigate to /blog

##Extra Details
Only the root route "/" generates 404, whilst other routes with extra uri parts works just fine.

##Documentation

• Fixed when registering a multilingual routes grouped in a prefix.
• Added test cases to test if it can register grouped routes with a prefix and if the routes exists.

[AbdullahFaqeir]

Hi @chinleung!

Can you please check and review the PR?

[chinleung]

Thanks @AbdullahFaqeir!

[AbdullahFaqeir]

@chinleung You're most welcome, and I'm more than happy to help anytime in the future, just ping.

[AbdullahFaqeir]

Hey @chinleung!

Can you please add 'hacktoberfest' to the repo's topics