message: Update README.md
  Tiny grammar fix.
diff: @@ -122,7 +122,7 @@ cargo build --release
  If all goes well, this should place a binary at `target/release/alacritty`.
  **BEFORE YOU RUN IT:** Install the config file as described below; otherwise,
  -many things (such as arrow keys) would not work. If you're on macOS, you'll need
  +many things (such as arrow keys) will not work. If you're on macOS, you'll need
  to change the `monospace` font family to something like `Menlo`.
  ### Desktop Entry
  