SFTPDocumentsProvider: append mount path to title

SFTPDocumentsProvider: do not add port to title if canonical

SFTPDocumentsProvider: add summary

SFTPDocumentsProvider: correct connection resetting

SFTPDocumentsProvider: proper error handling

SFTPDocumentsProvider: refactor toasting

reformat code

fix various lints

build: bump sshlib to 2.2.20

seekable reader, bump min sdk level to 26

build: modernize toolchain

README: we support custom path now

don't reuse SFTPv3Client, it's not costy and this enables concurrency

ReadTask: always try to close the file

add mount path settings

show configured values on create

adjust inputType

close connection on query roots

notify root change when config changes

NetworkOnMainThreadException workaround