chore: add std feature which provides Error impl

This should provide `Error` implementation for `CursorIconParserError`,
when the crate is used with `std`.

The `no_std` will require `core::error::Error`, which is not stable yet.

Author: notgull

.github/workflows/ci.yml

@@ -43,3 +43,6 @@ jobs:
 
       - name: Run tests
         run: cargo test --verbose
+
+      - name: Run tests with no default features
+        run: cargo test --verbose --no-default-features

Cargo.toml

@@ -12,4 +12,8 @@ categories = ["gui"]
 rust-version = "1.64.0"
 
 [dependencies]
-serde = { version = "1.0.162", default-features = false, features = ["derive"], optional = true }
+serde = { version = "1.0.162", default-features = false, features = ["derive"], optional = true }
+
+[features]
+default = ["std"]
+std = []

src/lib.rs

@@ -1,4 +1,4 @@
-#![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
 #![deny(rust_2018_idioms)]
 #![deny(rustdoc::broken_intra_doc_links)]
 #![deny(unsafe_op_in_unsafe_fn)]
@@ -319,3 +319,6 @@ impl core::fmt::Display for CursorIconParseError {
         f.write_str("failed to parse cursor icon")
     }
 }
+
+#[cfg(feature = "std")]
+impl std::error::Error for CursorIconParseError {}