feat: define the crate's MSRV

.github/workflows/ci.yaml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        rust: [stable]
+        rust: [stable, 1.34.0]
 
     steps:
     - uses: actions/checkout@master

README.md

@@ -49,6 +49,17 @@ The features available are:
 
 All of these are enabled by default.
 
+MSRV
+----
+
+Our current Minimum Supported Rust Version is **1.34.0**. When adding features,
+we will follow these guidelines:
+
+- We will always support the latest four minor Rust versions. This gives you a 6
+  month window to upgrade your compiler.
+- Any change to the MSRV will be accompanied with a **minor** version bump
+   - While the crate is pre-1.0, this will be a change to the PATCH version.
+
 Examples
 --------
 

src/types.rs

@@ -1,6 +1,5 @@
 //! Types that specify what is contained in a ZIP.
 
-#[non_exhaustive]
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum System {
     Dos = 0,