Current pull request contains patched `CHANGELOG.md` file for the
`v0.2.0` version.

Co-authored-by: GitHub Action <action@github.com>

From my testing, Toolbox forwards through SSH (i.e. through Coder) a
remote port associated with the IDE
running in server mode, to localhost in order for the server (i.e. the
remote IDE) to communicate with
JBClient. Unlike with Gateway, Toolbox manages to reuse the SSH
connection, and it doesn't open a separate
one for port forwarding.

From Gateway we inherited two ssh hostnames per each workspace, one for
background connections that did not
involve running IDEs. Coder discards the bg. connection from the
collected metrics in order to
avoid double counting. Since Toolbox manages to re-use the connection we
don't need to worry
about double counting.

For this particular change, I deployed the latest Coder version with
prometheus metrics and experiments
enabled (i.e. --prometheus-enable --prometheus-collect-agent-stats
--experiments=workspace-usage) and made the following experiment:

1. Opened up Toolbox, logged into Coder. At this point:
- agent_sessions_total and coderd_agentstats_session_count_jetbrains
were missing from prometheus metrics
- jetbrains session count from api/v2/deployment/stats showed 0

2. Opened up a Workspace at which point Toolbox established the SSH
connection:
- agent_sessions_total and coderd_agentstats_session_count_jetbrains
increased to 1
- jetbrains session count from api/v2/deployment/stats increased to 1 as
well

3. Hit the install button on RustRover, everything stayed unchanged

4. Open RustRover, nothing changes in the stats.

… while an SSH connection is alive.

Toolbox raises a class cast exception when Workspaces are stopped while
the SSH connection is running. After the workspace was stopped Toolbox
refused to show widget with some weird glitches on the screen.
The fix in this case is to safely disconnect the SSH before sending the
stop command to the workspace. The code will wait at most 10 seconds for
the disconnect to happen, and only after that send the stop.

- resolves #98

There is a brief moment between manual authentication and workspace
poller initialization and execution where we see a "No workspaces yet"
which is misleading. Instead, a loading indicator/message should be
displayed.

- resolves #103

The Settings menu is only available after we successfully authenticate.
This can be somewhat problematic if we want to configure something like
coder cli path, or certificate path before doing the authentication.

A new "Settings" button at the bottom of the page can now access the
Settings page. Toolbox is a bit inflexible with the API because:
- I could not find a way to delimit or separate the Settings button from
the Back and Sign In/Connect button
- we can't put a button or anything else in the top right corner, the
traditional place for a settings icon.

- resolves #90

Current pull request contains patched `CHANGELOG.md` file for the
`v0.2.1` version.

Co-authored-by: GitHub Action <action@github.com>