feat(material/card): support filled variant

[naaajii]

feat(material/card): support filled variant

this commit add filled variant for material card which provides subtle seperation from background and has less emphasis than elevated or outlined cards

fixes https://github.com/angular/components/issues/29840

---

docs(material/card): add each appearance example

update the example to contain elevated, outlined & filled variants

---

---

I tried to have a swing at this and it might be not perfect.