[illumos] fix name to be lowercase

Per special request from the illumos core dev. "illumos" is always written in
lowercase, because many fonts don't clearly distinguish between "I" and "l"
[1].

[1] https://github.com/TritonDataCenter/smartos-live/pull/217/files#r38812501

README.md

@@ -37,7 +37,7 @@ WhoAmI targets all platforms that can run Rust, including:
    - Web Browser - DOM
    - WASI (Wasite, others) **may partially or fully work - but untested**
    - Daku (Ardaku/Quantii, others) **mock implementation, full implementation planned later**
- - Illumos variants (SmartOS, OmniOS, others) **may partially or fully work - but untested**
+ - illumos variants (SmartOS, OmniOS, others) **may partially or fully work - but untested**
  - Android **may partially or fully work - but untested, planned later**
  - iOS **planned later**
  - Redox **planned later**

src/lib.rs

@@ -186,7 +186,7 @@ pub enum DesktopEnv {
     Lxde,
     /// Stacking window manager for X Windows on Linux
     Openbox,
-    /// Desktop environment for Linux, BSD and Illumos
+    /// Desktop environment for Linux, BSD and illumos
     Mate,
     /// Lightweight desktop enivornment for unix-like operating systems
     Xfce,
@@ -279,7 +279,7 @@ impl Display for Platform {
             Self::Bsd => "BSD",
             Self::Windows => "Windows",
             Self::MacOS => "Mac OS",
-            Self::Illumos => "Illumos",
+            Self::Illumos => "illumos",
             Self::Ios => "iOS",
             Self::Android => "Android",
             Self::Nintendo => "Nintendo",