Clarify the keystore usage

[dandv]

Is your feature request related to a problem? Please describe.
For web developers unfamiliar with android, the keystore may be confusing.

Describe the solution you'd like
While running bubblewrap build,

? Password for the Key Store

can be interpreted as both "What is the password for the keystore", and "Set a password for the keystore"

Same for

? Password for the Key:

The previous prompts are ambiguous as well. I ended up creating a directory ("store"):

? Key store location: ./android.keystore
? Key name: ./android.keystore

Then I got this error,

Failed to load signer "signer #1"
java.io.FileNotFoundException: ./android.keystore (Is a directory)

Describe alternatives you've considered
PWABuilder?

Additional context
Ideally, a web dev who's never touched Android development, should be able to build a TWA from their PWA.

[andreban]

Regarding the key store location and name prompts, we recently introduced an explanation right before the questions. There's a bug where the default alias should be android instead of ./android.keystore. Builds still work though.

We could add more context when asking for the passwords during the build step, similar to the above.

[andreban]

#255 will fix using the correct alias by default.