Make mat-chip editable

#### Bug, feature request, or proposal:
Feature request

#### What is the expected behavior?
Editable filter chips (this existed in AngularJS Material)

#### What is the current behavior?
Readonly filter chips

#### What is the use-case or motivation for changing an existing behavior?
Editing a chip can be done in less keystrokes compared to deleting a chip and adding a new one. Sometimes, you have to delete bunch of chips to edit one chip.

For example, if you have:
(foo: bar) (OR) (foo2: bar2)

and you want to go to

(foo3: bar) (OR) (foo2: bar2)

User might choose to delete all chips and start over

L’issue mentionne le composant mat-chip, mais ne fournit aucun chemin vers un fichier source ou de test. Commencez par localiser mat-chip et son comportement filter-chip existant, puis examinez la documentation associée du composant et les tests avant de proposer l’interaction de modification. Done doit permettre aux utilisateurs de modifier la valeur d’un chip sans supprimer ni recréer le chip.

Rédigé par le modèle d'indexation à partir du texte de l'issue.