Set maximum (non-code) line length of Markdown texts to 80

Author: tesaguri

.editorconfig

@@ -0,0 +1,2 @@
+[*.md]
+max_line_length = 80

oauth-credentials/README.md

@@ -11,18 +11,20 @@
 
 ## Stability
 
-The goal of `oauth-credentials` is to provide a stable foundation for OAuth implementations.
+The goal of `oauth-credentials` is to provide a stable foundation for OAuth
+implementations.
 
-The crate is still unstable in the sense of Semantic Versioning. However, we are not planning to
-make any breaking change and are going to publish the API as it is as version 1.0.0 using the
-[semver trick] unless we find a flaw in the API significant enough to justify a breaking change.
+The crate is still unstable in the sense of Semantic Versioning. However, we
+are not planning to make any breaking change and are going to publish the API
+as it is as version 1.0.0 using the [semver trick] unless we find a flaw in the
+API significant enough to justify a breaking change.
 
 [semver trick]: https://github.com/dtolnay/semver-trick
 [#5]: https://github.com/tesaguri/oauth1-request-rs/pull/5
 
 While you should not use it as a public dependency of a stable crate yet
-(see [C-STABLE] of Rust API Guidelines), it is ready as a public dependency of an unstable crate
-and as a private dependency of a stable crate.
+(see [C-STABLE] of Rust API Guidelines), it is ready as a public dependency of
+an unstable crate and as a private dependency of a stable crate.
 
 [C-STABLE]: https://rust-lang.github.io/api-guidelines/necessities.html#public-dependencies-of-a-stable-crate-are-stable-c-stable
 
@@ -39,8 +41,9 @@ Feature | MSRV
 `serde` |  1.13.0
 `alloc` (without `std`) | 1.36.0
 
-Note that if your crate uses the `serde` feature (even if optionally!), it cannot be compiled
-directly with Rust 1.7.x and older due to [rust-lang/cargo#3763], but it can somehow be compiled as
-a non-root node of a dependency tree.
+Note that if your crate uses the `serde` feature (even if optionally!), it
+cannot be compiled directly with Rust 1.7.x and older due to
+[rust-lang/cargo#3763], but it can somehow be compiled as a non-root node of a
+dependency tree.
 
 [rust-lang/cargo#3763]: https://github.com/rust-lang/cargo/issues/3763