Bump version to 0.19.0

This change bumps the crate to version 0.19.0. The following notable
changes have been made since 0.18.0:
- Added ApiInfo::from_parts constructor
- Adjusted Client::issue to accept request input via reference
- Introduced ConversionError type
  - Replaced unwraps with proper error variants
- Updated ActivityType enum to be in sync with upstream variants
- Added support for unknown ActivityType variants
- Switched to using thiserror crate for defining error types
- Updated num-decimal to use version 0.4 of the num-* crates
- Bumped minimum supported Rust version to 1.46
- Bumped http-endpoint dependency to 0.5
- Bumped websocket-util dependency to 0.8
- Bumped tokio-tungstenite dependency to 0.14

CHANGELOG.md

@@ -1,5 +1,5 @@
-Unreleased
-----------
+0.19.0
+------
 - Added `ApiInfo::from_parts` constructor
 - Adjusted `Client::issue` to accept request input via reference
 - Introduced `ConversionError` type

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "apca"
-version = "0.18.0"
+version = "0.19.0"
 edition = "2018"
 authors = ["Daniel Mueller <[email protected]>"]
 license = "GPL-3.0-or-later"