v2.2: various things

This release includes some changes to the underlying architecture and some optional setup helpers.
Changelog (at least as I remember it, there might be smaller changes I totally forgot about):

• .NET 8 (LTS) runtime
• Everything is stored in the database now, even migrations are provided!
  don't forget to update the DB when migrating to this version
• Better (?) architecture, inspired by the similar rewrite of a sister project
  way less singletons, shorter lifecycles in general
• An option to auto-generate the bot menu shown in dialogs with the bot
• Home page with a minigame
• Epic glorious error page
  shared with my other web projects
• Retry-After header to give the clients a hint how long to wait before retrying

v2.1: Sometimes a picture is worth a thousand words

Small release that adds one feature -- instead of text messages, it's now possible to use stickers as notifications.

Use sticker instead of message in requests, to get ID of a sticker, just send it to the bot.

v2.0: The long-awaited sequel

It's a brand new update! About four and a half years since last release, time sure flies.
This is a combination of three separate attempts to modernize the app since its release in 2018.

Changes include:

• Brand new .NET 7 support!
• Actually proper markdown parsing this time! Separate markdown and plaintext parsing modes!
• An ability to send silent notifications!
• HTTP status codes instead of custom error messages!
• Async things!
• Probably something else I forgot about in these years!

See the updated readme for details. The parsing changes are somewhat breaking, hence the major version increment.

Migration from v1.2 is mostly appsettings.json editing: "Strings" section is removed, "ApiEndpointUrl" should no longer include the "/api" part itself, and the connection string is updated.

v1.2: Now everything horribly breaks less often

• Fixes markdown parsing issues where simple strings like send_help passed to web API are considered malformed Markdown and are dropped by Telegram API.
• Formatting changed:
  • now accepts same Markdown flavor that is used in Telegram clients: **bold** for bold, __italic__ for italic
  • < and > should be escaped as > and < or message might be dropped or rendered incorrectly (because I'm bad at programming)

These API changes are somewhat breaking: clients that use Markdown and not plaintext should be updated.

Initial release: look ma, I can write ASP.NET Core apps!

Version 1.0.0.0, works on my machine™.
Linux-only release. (for now? forever? 🤔)