Document that `AcceptedSecretArns` supports friendly names & partial ARN's

[kpenergy]

The SecretsManagerConfigurationProviderOptions.AcceptedSecretArns property's name suggests that it only supports full ARN's. However, the value's specified here are used as the SecretId in a GetSecretValueRequest, which means they can be:

• Full ARN (including random 6 characters at end)
• Partial ARN (excluding random 6 characters at end)
• Friendly Name

It would be good if either:

• The property name could be updated to remove the word ARN, since it's not specific to ARNs (I doubt this is a feasible option since it's a breaking change).
• Add XML documentation on this property (and ideally, on all properties, methods etc).
• Add more information in the relevant README section to let users know what can be used here

[Kralizek]

Hi @kpenergy

Thanks for opening this issue. Right now I don't have the time to invest in this library but I welcome contributors to propose changes with PRs: this applies both to the source code and to the documentation.

[kpenergy]

@Kralizek No worries, I'll try and submit an update to the docs over the next few days.

[devklick]

Created PR #60 to update docs and comments