Add package usage instructions for cabal

INSTALL.md

@@ -0,0 +1,81 @@
+# Using `streamly` package
+
+The latest stable release of the package is available 
+[on Hackage](https://hackage.haskell.org/package/streamly). You can also try
+the latest development version 
+[from github](https://github.com/composewell/streamly).
+
+The default version available to you and how to pick a specific version may
+depend on the build tool you are using. We have provided instructions to use a
+specific version for some tools below.
+
+## cabal
+
+Make sure you have `cabal` version 2.4 or later installed and you have `ghc`
+available in your PATH. Refresh your package list:
+
+```
+$ cabal v2-update
+```
+
+### hackage version in repl
+
+```
+# Pick the latest version on Hackage
+$ cabal v2-repl --build-depends streamly
+
+# Pick a specific version on Hackage
+$ cabal v2-repl --build-depends streamly==0.6.1
+```
+
+### github version in repl
+
+Create a `test` directory and create a `cabal.project` file in it as follows:
+
+```
+packages: .
+source-repository-package
+  type: git
+  location: https://github.com/composewell/streamly
+  tag: master
+```
+
+Create a `test.cabal` file as follows
+
+```
+cabal-version: 2.4
+name: test
+version: 0
+
+library
+  build-depends: base, streamly
+```
+
+Run repl:
+
+```
+$ cabal v2-repl
+```
+
+### ghc
+
+```
+$ cat hello.hs
+import qualified Streamly.Prelude as S
+
+main = S.runStream $ S.fromListM [putStrLn "hello", putStrLn "world"]
+```
+
+```
+$ cabal v2-install streamly-0.6.1
+$ ghc -package streamly-0.6.1 hello.hs
+```
+
+### Project
+
+Add `streamly` to the `build-depends` section of your library/executable in
+your `<package>.cabal` file. Appropriate version from Hackage will be picked
+depending on the version bounds that you specify. See the `github version in
+repl` section above for a sample `<package>.cabal` file and optionally the
+`cabal.project` file if you want to use the development version from github in
+your project.