feat: authentication capabilities

[vobu]

authentication capabilities:

• BTP SAP Cloud IdP
• BTP Standard IdP
• Office 365
• Basic Auth
• custom auth fields

authentication works for single browser scenarios as well as multiremote.

credentials and authentication types are provided at design-time through configuration and don't require code changes.
docs still todo, short version is:

• standard: provide env vars wdi5_username and wdi5_password w/ respective values
• multiremote: provide env var swdi5_$remote-id_username and wdi5_$remote-id_password w/ respective values
• add wdi5:authentication config object (see src/types/wdi5.types.ts → *Authenticator) to the capabilities section of the wdio.conf.(t|j)s file

addressing #207

[Siolto]

throw error when obligatory parameters for custom auth are missing, needs to be implemented.