Add ability to buffer output of `newEncoderFeed` and `newDecoderFeed`

[05nelsonm]

e.g.

val sb = StringBuilder()

Base32.Default.newEncoderFeed(CharBufferOutFeed { buf, len ->
    sb.appendRange(buf, 0, len)
}).use { feed ->
    // ...
}

Base32.Default.newBufferedDecoderFeed(ByteBufferOutFeed(size = 8096) { buf, len ->
    // ...
}).use { feed ->
    // ..
}

Need to think about how this will play with the LineBreakOutFeed

[05nelsonm]

Closing. Primary reason for utilizing a Feed in the first place is to direct the output to the desired medium (file, http request, etc.). If a buffer is needed with a feed, caller can easily setup their own.