Add example OSX user agent service (#86)

* feat: add osx launchd agent example

* fix: spelling

* chore: Update README.md

* Update ra-mux.plist to include all cargo and rust-analyzer likely installations paths

Co-authored-by: Jihyeon Kim (김지현) <simnalamburt@gmail.com>

* Update ra-mux.plist to start automatically

Co-authored-by: Jihyeon Kim (김지현) <simnalamburt@gmail.com>

* Update README.md to clarify that ra-mux can run as a user service

---------

Co-authored-by: Jihyeon Kim (김지현) <simnalamburt@gmail.com>

Author: pplanel

README.md

@@ -56,7 +56,9 @@ Options:
   -V, --version  Print version
 ```
 
-`ra-multiplex server` can run as a systemd user service, see the example `ra-mux.service`.
+`ra-multiplex server` can run as a user service:
+* On `systemd` available systems see the example `ra-mux.service`.
+* On `OSX Launchd` systems see the example `ra-mux.plist`
 
 Configure your editor to use `ra-multiplex` as `rust-analyzer`, for example for
 CoC in neovim edit `~/.config/nvim/coc-settings.json`, add:

ra-mux.plist

@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+  <dict>
+    <key>Label</key>
+    <string>com.github.ra-multiplex</string>
+    <key>ProgramArguments</key>
+    <array>
+      <string>[PATH_TO_BIN]</string>
+      <string>server</string>
+    </array>
+    <key>EnvironmentVariables</key>
+    <dict>
+      <key>PATH</key>
+      <string>/opt/homebrew/bin:/opt/homebrew/sbin:/usr/bin:/bin:/usr/sbin:/sbin:[HOME]/.cargo/bin</string>
+    </dict>
+    <key>StandardOutPath</key>
+    <string>/tmp/ra-multiplex.log</string>
+    <key>StandardErrorPath</key>
+    <string>/tmp/ra-multiplex.log</string>
+    <key>KeepAlive</key>
+    <true />
+    <key>RunAtLoad</key>
+    <true/>
+    <key>LimitLoadToSessionType</key>
+    <array>
+      <string>Aqua</string>
+      <string>Background</string>
+      <string>LoginWindow</string>
+      <string>StandardIO</string>
+      <string>System</string>
+    </array>
+    <key>UserName</key>
+    <string>[USERNAME]</string>
+    </dict>
+  </plist>
+