MacTex 2020.0407 - Making it clear you need to restart your terminal to use (#82283)

* MacTex - Making it clear you need to restart your terminal to use

* fix style error

* Responding to PR feedback

* Update mactex.rb

Co-authored-by: Chris Paika <cpaika@constantcontact.com>
Co-authored-by: Vítor Galvão <info@vitorgalvao.com>

Casks/mactex.rb

@@ -75,4 +75,11 @@ cask 'mactex' do
                '/usr/local/texlive',
                '~/Library/texlive',
              ]
+
+  caveats <<~EOS
+    You must restart your terminal window for the installation of MacTex CLI tools to take effect.
+    Alternatively, Bash and Zsh users can run the command:
+
+      eval "$(/usr/libexec/path_helper)"
+  EOS
 end