* Fix accessibility of column headers

As a screen reader user new to Mastodon, I encountered the following issues with the column headers as designed:
 * Jumping between them was difficult. FOr instance, passing my home timeline to reach notification settings was difficult to impossible, especially considering infinite scrolling.
 * There doesn't appear to be any means for triggering the control via the keyboard. the `titleClick` handler only responds to mouse clicks.
 * I didn't even realize there was a Settings toggle until I made this change.

Thanks for using ARIA in your designs. It's a huge help. But adding a `button` role doesn't add keyboard handling and other button behavior. Also, because the role was on the heading container, it obscured the controls within the container itself. This fix resolve that. It also exposes the headings as headings rather than buttons, enabling skipping columns by using screen readers' heading navigation commands.

Since I myself am blind, if this fix requires additional visual styling, I'd like help applying that so it can be merged. I'd consider it an essential accessibility fix for my and other blind users' existence on the platform. Thanks!

* Styling fixes

* Fixed overflow issue

SCSS Refactor

Add glitchy elephant friend

This makes the clickable element an interactive element, but doesn't add
alt text and makes it not-obvious that you can click the elefriend.  On
one hand, this goes against good practice; on the other hand, it's not
*supposed* to be obvious that you can click the elefriend.

Also lay some groundwork needed to interactively change the
glitchfriend.

The codebase uses "elefriend" because it's shorter and didn't require me
to realign the actions in actions/compose.js.  Same idea, though.

Glitched elephant friends kindly provided by @ncls7615.

Load public javascripts on admin pages

i18n: Update Polish translation

Signed-off-by: Marcin Mikołajczak <me@m4sk.in>

Fix dropdown item text

* Handle sessions that can't be translated

This commit fixes #6165.

* Fix typo

dockerfile: Give more stack space to /sbin/tini

/sbin/tini ends up running the Sass compiler, which seems to need a
larger thread stack size than the musl default.  This patch incorporates
a fix from
https://raw.githubusercontent.com/jubel-han/dockerfiles/master/common/stack-fix.c,
as described in https://github.com/sass/node-sass/issues/2031.

Fix #317: Attempting to switch flavors raises ActionController::ParameterMissing

If a flavour has only one skin, the skin selector will be omitted.  This
omits the user[setting_skin] field, and because that's the only
user[...] field on the page, the entire user object will not be present
in the request handler's params object.

This commit accounts for that scenario by avoiding params.require(:user)
and instead picking out what we need from the params hash.

Fix glitch async chunks

Merge vanilla updates into glitch - round 2