Add FreeBSD CI details to README and cabal file

Author: harendra-kumar

README.md

@@ -31,7 +31,7 @@ to your package repo
   [.circleci/config.yml](https://github.com/composewell/packcheck/blob/master/.circleci/config.yml)
   to your package repo
 
-#### Appveyor
+#### Appveyor (Windows)
 * Add your package repo to Appveyor as necessary (See
   https://www.appveyor.com/docs/server/)
 * Copy
@@ -45,6 +45,13 @@ to your package repo
   [.github/workflows/packcheck.yml](https://github.com/composewell/packcheck/blob/master/.github/workflows/packcheck.yml)
   to your package repo
 
+#### Cirrus (FreeBSD)
+* Add your package repo to Cirrus as necessary (See
+  https://cirrus-ci.org/)
+* Copy
+  [.cirrus.yml](https://github.com/composewell/packcheck/blob/master/.cirrus.yml)
+  to your package repo
+
 CI should work out of the box for most packages. Uncomment the relevant lines
 in the CI config files or change the values of the environment variables for
 fine grained control or custom configuration.

packcheck.cabal

@@ -4,11 +4,11 @@ synopsis:           Universal build and CI testing for Haskell packages
 description:
   This package contains a universal CI/build script @packcheck.sh@ and config
   files designed such that you can just copy over
-  @.github\/workflows/packcheck.yml@, @appveyor.yml@ or @.circleci/config.yml@
-  to your package repo and your package is CI ready
-  in a jiffy.  You can build and test packages on local machine as well. For
-  local testing, copy @packcheck.sh@ to your local machine, put it in your
-  PATH, and run it from your package directory:
+  @.github\/workflows/packcheck.yml@, @appveyor.yml@, @.circleci/config.yml@
+  or @.cirrus.yml@ to your package repo and your package is CI ready
+  in a jiffy.  You can build and test packages on local machine as
+  well. For local testing, copy @packcheck.sh@ to your local machine,
+  put it in your PATH, and run it from your package directory:
   .
   > $ packcheck.sh cabal
   > $ packcheck.sh stack