docs: Add note abuout rewrite in README

In order to enable users to be aware about our
rewrite, and still be able to see the code of
karma-webpack, adding a note in our README.

README.md

@@ -30,6 +30,7 @@
   </a>
   <h1>Karma Webpack</h1>
   <p>Use webpack to preprocess files in karma<p>
+  <p><b>Note:</b> At the moment we are doing a complete rewrite of karma-webpack. The code behind the current version is on the branch [v1](https://github.com/webpack/karma-webpack/tree/v1) in this repo. We will continue maintaining it in the mean time.</p>
 </div>
 
 <h2 align="center">Install</h2>
@@ -266,4 +267,4 @@ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-THE SOFTWARE.
+THE SOFTWARE.