pgAdmin 4 commit: 1) Ensure that path file name should not disappear wh

1) Ensure that path file name should not disappear when changing ext from the dropdown in file explorer dialog. Fixes
#3812.
2) Fix column resizable issue in the file explorer dialog. Fixes #4827.

Used tablesorter's resizable widget.

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=8b99a33e6ec2d351d866a09b64e4d3c60f6ad939
Author: Aditya Toshniwal <aditya.toshniwal@enterprisedb.com>

Modified Files
--------------
docs/en_US/release_notes_4_18.rst                  |   2 +
web/package.json                                   |   2 +-
.../misc/file_manager/static/css/file_manager.css  |   4 +-
web/pgadmin/misc/file_manager/static/js/utility.js | 453 ++++++++++++---------
.../file_manager/static/scss/_file_manager.scss    |  41 +-
web/pgadmin/static/scss/_pgadmin.style.scss        |  21 +-
web/yarn.lock                                      |   8 +-
7 files changed, 298 insertions(+), 233 deletions(-)