Bump MSRV to 1.66.0

This is to gain access to `BTreeMap::first_key_value` and `BTreeMap::last_key_value`.

It was released over a year ago, so hopefully that won't affect anyone.
I guess we should set a formal MSRV policy at some point.

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         toolchain:
           # Don't forget to update the README when bumping MSRV.
-          - 1.65.0
+          - 1.66.0
           - stable
           - beta
           - nightly

CHANGELOG.md

@@ -1,7 +1,7 @@
 ### v1.5.0 (unreleased)
 
 - **Changes**:
-    - Bump minimum supported Rust version to 1.65.0 (released 2022-11-03). This is for compatibility with new versions of some of rangemap's test dependencies.
+    - Bump minimum supported Rust version to 1.66.0 (released 2022-12-15). This is to gain access to `BTreeMap::first_key_value` and `BTreeMap::last_key_value`, and for compatibility with new versions of some of rangemap's test dependencies.
     - TODO: All of xfbs's PRs!
 
 ### v1.4.0 (2023-09-19)

Cargo.toml

@@ -14,7 +14,7 @@ Map and set data structures whose keys are stored as ranges.
 Contiguous and overlapping ranges that map to the same value are coalesced into a single range.
 """
 categories = ["data-structures"]
-rust-version = "1.65.0"
+rust-version = "1.66.0"
 
 [dependencies]
 serde = { version = "1", optional = true }

README.md

@@ -3,7 +3,7 @@
 [![Crate](https://img.shields.io/crates/v/rangemap.svg)](https://crates.io/crates/rangemap)
 [![Docs](https://docs.rs/rangemap/badge.svg)](https://docs.rs/rangemap)
 [![Build status](https://github.com/jeffparsons/rangemap/workflows/CI/badge.svg)](https://github.com/jeffparsons/rangemap/actions)
-[![Rust](https://img.shields.io/badge/rust-1.65.0%2B-blue.svg?maxAge=3600)](https://github.com/jeffparsons/rangemap) <!-- Don't forget to update the GitHub actions config when bumping minimum Rust version. -->
+[![Rust](https://img.shields.io/badge/rust-1.66.0%2B-blue.svg?maxAge=3600)](https://github.com/jeffparsons/rangemap) <!-- Don't forget to update the GitHub actions config when bumping minimum Rust version. -->
 
 [`RangeMap`] and [`RangeInclusiveMap`] are map data structures whose keys
 are stored as ranges. Contiguous and overlapping ranges that map to the same