Add v0-specific change descriptions

[ecraig12345]

If a package is a 0.x version, the default prompt now looks like this:

Patch      - bug fixes; new features; backwards-compatible API changes (ok in patches for version < 1)
Minor      - breaking changes; major feature (ok in minors for version < 1)
None       - this change does not affect the published package in any way
Major      - official release

Wording for v1+ packages has been slightly tweaked as well:

Patch      - bug fixes; no API changes
Minor      - new feature; backwards-compatible API changes
None       - this change does not affect the published package in any way
Major      - breaking changes; major feature

The messages can also now be easily customized using BeachballOptions.changeFilePrompt.changeTypeDescriptions.