Add release notes for `v0.9.0`

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+---
+title: "Release v0.9.0"
+description: "Announcing the v0.9.0 release of BDK"
+authors:
+    - Alekos Filini
+date: "2021-07-11"
+tags: ["rust", "release"]
+hidden: true
+draft: false
+---
+
+A new release of BDK is out: [`v0.9.0`] brings support for Bitcoin Core backends, more sanity checks and bugfixes.
+
+You can find the full [v0.9.0 changelog][changelog] on GitHub.
+
+## What's new in v0.9.0
+
+Below are some highlights of the new release:
+
+## Bitcoin Core `Blockchain` Backend
+
+This release finally adds support for using a Bitcoin Core node as the `Blockchain` backend for a wallet, through the RPC. This is still considered experimental for the time being, since there are a few missing
+things that we'd like to add, and adding those could force us to change the API a little.
+
+Nonetheless, if you don't mind a breaking-change later on it's already fully functional.
+
+The backend works by importing addresses in Bitcoin Core using the `importmulti` call.
+
+Using it is pretty straightforward, here's a quick example:
+
+```rust
+let config = RpcConfig {
+    url: "127.0.0.1:18332".to_string(),
+    auth: bitcoincore_rpc::Auth::CookieFile("/home/user/.bitcoin/.cookie".into()),
+    network: bdk::bitcoin::Network::Testnet,
+    wallet_name: "wallet_name".to_string(),
+    skip_blocks: None,
+};
+let blockchain = RpcBlockchain::from_config(&config);
+```
+
+Similarly to the compact filters backend, the `skip_blocks` field allows for starting a rescan of the blockchain at a given height rather than the genesis, saving some time. The rescan is only performed once, the
+first time an address is imported. Afterwards every `sync()` call will only perform a few queries on the node and it will be much faster.
+
+## Updated `TransactionDetails` Struct
+
+To better accomodate the Bitcoin Core RPC and potentially more future new backends, the [`TransactionDetails`] structure have been updated as follows:
+
+- The `fees` field has been renamed to `fee` and it has been made optional. `Blockchain` backends can set this to `None` when they have no way of computing the fee of a transaction
+- The `timestamp` and `height` fields have been merged into an optional [`ConfirmationTime`] struct
+
+## Verify Downloaded TXs
+
+This release also introduces an opt-in feature called `verify` that can be enabled to verify the unconfirmed transactions that BDK downloads from untrusted sources like Electrum servers.
+
+Verifying the transactions against the consensus rules can be an additional protection against some kind of attacks that could trick a wallet into creating wrong RBF (BIP 125) "bump" transactions. Check out [the issue][issue_verify]
+for more details.
+
+## Contributors
+
+A huge thanks to everybody who contributed to this new release with suggestions, pull requests and bug reports.
+
+Since the `v0.8.0` release around a month ago, we've had `45` new commits made by `6` different contributors for a total of `1336` additions and `266` deletions. Here's the [full diff][gh_diff].
+
+A special thanks to the new contributor for this release:
+
+- [@jb55][@jb55] - William Casarin
+
+[changelog]: https://github.com/bitcoindevkit/bdk/blob/7a9b691f68c41116dc7857bc0267a2e3b2eafdd3/CHANGELOG.md
+[gh_diff]: https://github.com/bitcoindevkit/bdk/compare/v0.8.0...v0.9.0
+
+[issue_verify]: https://github.com/bitcoindevkit/bdk/issues/352
+
+[`TransactionDetails`]: https://docs.rs/bdk/0.9.0/bdk/struct.TransactionDetails.html
+[`ConfirmationTime`]: https://docs.rs/bdk/0.9.0/bdk/struct.ConfirmationTime.html
+
+[`v0.9.0`]: https://crates.io/crates/bdk/0.9.0