feat: implement the loading indicator component

[adrcotfas]

• The goal is to implement a loading indicator. This component is similar but not the same as progress indicators. The modern expressive version uses a set of shapes and morphing between them.
• Reuse the shapes added in feat: add Material Expressive Shapes #4984
• See https://m3.material.io/components/loading-indicator/specs
• Reuse newly introduced tokens (shape, motion, typography, color etc)
• Extract component specific tokens for easier maintenance.
• Get inspired from TextInput/TextField, Switch, Checkbox, FAB components which have gone through modernization.
• Showcase the component in the example app
• Update the documentation