Add keyboard shortcuts dialog

[TheEvilSkeleton]

Description

This includes parts of #2683

[github-actions]

Pylint result on modfied files:

************* Module bottles.frontend.main
bottles/frontend/main.py:211:0: C0303: Trailing whitespace (trailing-whitespace)
bottles/frontend/main.py:32:0: C0413: Import "from gi.repository import Gtk, Gio, GLib, GObject, Adw" should be placed at the top of the module (wrong-import-position)
bottles/frontend/main.py:32:0: E0611: No name 'Adw' in module 'gi.repository' (no-name-in-module)
bottles/frontend/main.py:34:0: W0401: Wildcard import bottles.frontend.params (wildcard-import)
bottles/frontend/main.py:34:0: C0413: Import "from bottles.frontend.params import *" should be placed at the top of the module (wrong-import-position)
bottles/frontend/main.py:35:0: C0413: Import "from bottles.backend.logger import Logger" should be placed at the top of the module (wrong-import-position)
bottles/frontend/main.py:36:0: C0413: Import "from bottles.frontend.windows.main_window import MainWindow" should be placed at the top of the module (wrong-import-position)
bottles/frontend/main.py:37:0: C0413: Import "from bottles.frontend.views.preferences import PreferencesWindow" should be placed at the top of the module (wrong-import-position)
bottles/frontend/main.py:38:0: C0413: Import "from bottles.backend.health import HealthChecker" should be placed at the top of the module (wrong-import-position)
bottles/frontend/main.py:49:0: C0103: Constant name "base_dir" doesn't conform to UPPER_CASE naming style (invalid-name)
bottles/frontend/main.py:171:12: R1722: Consider using 'sys.exit' instead (consider-using-sys-exit)
bottles/frontend/main.py:177:12: W0105: String statement has no effect (pointless-string-statement)
bottles/frontend/main.py:215:12: C0415: Import outside toplevel (subprocess) (import-outside-toplevel)
bottles/frontend/main.py:217:12: R1732: Consider using 'with' for resource-allocating operations (consider-using-with)
bottles/frontend/main.py:221:12: C0415: Import outside toplevel (bottles.frontend.windows.bottlepicker.BottlePickerDialog) (import-outside-toplevel)
bottles/frontend/main.py:267:8: R1722: Consider using 'sys.exit' instead (consider-using-sys-exit)
bottles/frontend/main.py:258:0: W0613: Unused argument 'args' (unused-argument)
bottles/frontend/main.py:270:15: W0613: Unused argument 'action' (unused-argument)
bottles/frontend/main.py:270:28: W0613: Unused argument 'param' (unused-argument)
bottles/frontend/main.py:280:24: W0613: Unused argument 'action' (unused-argument)
bottles/frontend/main.py:280:37: W0613: Unused argument 'param' (unused-argument)
bottles/frontend/main.py:290:0: W0613: Unused argument 'args' (unused-argument)
bottles/frontend/main.py:294:0: W0613: Unused argument 'args' (unused-argument)
bottles/frontend/main.py:297:4: W1113: Keyword argument before variable positional arguments list in the definition of __show_importer_view function (keyword-arg-before-vararg)
bottles/frontend/main.py:297:35: W0613: Unused argument 'widget' (unused-argument)
bottles/frontend/main.py:297:0: W0613: Unused argument 'args' (unused-argument)
bottles/frontend/main.py:280:4: W0238: Unused private member `Bottles.__refresh(self, action=None, param=None)` (unused-private-member)
bottles/frontend/main.py:254:8: W0201: Attribute 'win' defined outside __init__ (attribute-defined-outside-init)
bottles/frontend/main.py:388:9: W0613: Unused argument 'version' (unused-argument)
bottles/frontend/main.py:20:0: C0411: standard import "os" should be placed before third party import "gi" (wrong-import-order)
bottles/frontend/main.py:21:0: C0411: standard import "gettext" should be placed before third party import "gi" (wrong-import-order)
bottles/frontend/main.py:22:0: C0411: standard import "locale" should be placed before third party import "gi" (wrong-import-order)
bottles/frontend/main.py:23:0: C0411: standard import "webbrowser" should be placed before third party import "gi" (wrong-import-order)
bottles/frontend/main.py:24:0: C0411: standard import "os.path" should be placed before third party import "gi" (wrong-import-order)
bottles/frontend/main.py:20:0: W0611: Unused import os (unused-import)
bottles/frontend/main.py:34:0: W0614: Unused import(s) APP_NAME_LOWER, BASE_ID, PROFILE, ANIM_DURATION, EXECUTABLE_EXTS and DOC_URL from wildcard import of bottles.frontend.params (unused-wildcard-import)