Reword and give examples in digest.base64_encode

[TarantoolBot]

Reword and give examples in digest.base64_encode

https://www.tarantool.io/en/doc/latest/reference/reference_lua/digest/#digest-base64-encode

• Take a usual string which converts to base64 with + and /
• give examples of output without options and with each of the options

---

<…> or line feed, and may contain
‘-‘ or ‘_’ instead of ‘+’ or ‘/’ |for positions 62 and 63 in the index
table|.

Options may be true or false, the default value is false.
For<…>

https://www.tarantool.io/en/doc/latest/reference/reference_lua/digest/#digest-base64-encode

It seems, it refers to the implementation details, which are not available for a user.