chore: create rustfmt.toml, update CI to use nightly for fmt job

Author: luisschwab

.github/pull_request_template.md

@@ -20,7 +20,7 @@ of the PR were done in a specific way -->
 
 * [ ] I've signed all my commits
 * [ ] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
-* [ ] I ran `cargo fmt` and `cargo clippy` before committing
+* [ ] I ran `cargo +nightly fmt` and `cargo clippy` before committing
 
 #### New Features:
 

.github/workflows/cont_integration.yml

@@ -126,7 +126,6 @@ jobs:
         run: cargo check --target wasm32-unknown-unknown --no-default-features --features bdk_core/hashbrown,async
 
   fmt:
-    needs: prepare
     name: Rust fmt
     runs-on: ubuntu-latest
     steps:
@@ -137,12 +136,12 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-            toolchain: ${{ needs.prepare.outputs.rust_version }}
+            toolchain: nightly
             override: true
             profile: minimal
             components: rustfmt
       - name: Check fmt
-        run: cargo fmt --all -- --config format_code_in_doc_comments=true --check
+        run: cargo fmt --all --check
 
   clippy_check:
     needs: prepare

rustfmt.toml

@@ -0,0 +1,3 @@
+comment_width = 100
+format_code_in_doc_comments = true
+wrap_comments = true