Playground CLI improvements

[adamziel]

Let's review these, and other wp-now bug reports/feature requests, and use them to improve Playground CLI:

• wp-now: support yml for blueprints playground-tools#313
• wp-now: blueprint override (like wp-env.override.json) playground-tools#312
• wp-now: additional "plugins" mode playground-tools#311
• wp-now: blueprints doesnt cache plugins/themes  playground-tools#309
• wp-now: .env support playground-tools#306
• wp-now: wp-cli step doesnt work in wp-content mode playground-tools#304
• wp-now: the blueprint json schema requires both php AND wp version  playground-tools#303
• wp-now: preferred php version from blueprint.json will be ignored in wp-content mode playground-tools#302

[orballo]

Is Playground CLI going to be an alternative to wp-now?

[adamziel]

@orballo that's the plan eventually, although I don't have any timeline to offer. With work like #1608, Playground will gradually absorb features like autodetection of directory contents.