Use cargo make to run tests for examples

[agilarity]

This makes it easier to run checks and tests for all examples.

It also covers the cargo make part of #210.

The Solution:

• Makes the examples directory a workspace
• Adds task flows that support lint, unit, and web testing
• Makes web testing optional
• Demonstrates calling from the leptos workspace

Run cargo make test-examples in the root to verify.

The counters example is excluded from the members until the test compile errors are fixed.

[gbj]

Thanks! This looks good to me.