Add proper readme

CHANGELOG.md

@@ -1,4 +1,5 @@
 # Changelog for profold
 
 ## Upcoming
+* add readme
 * create project

README.md

@@ -1 +1,22 @@
 # profold
+
+This project is a terminal-based viewer for ghc `.prof` files. These files are
+the result of profiling with `+RTS -p`, and can easily be thousands of lines
+long. This makes it cumbersome to browse through them and find the interesting
+bits.
+
+Since `.prof` files have a tree-like structure, an obvious improvement for
+viewing them is folding and unfolding parts of the tree, which is what profold
+allows you to do.
+
+![profold showing a profile of profold](screenshot.png)
+
+## Usage
+
+Open a file with profold:
+```
+$ profold file_to_open.prof
+```
+
+Arrow keys or vim-like keybindings to navigate. Tab to fold or unfold the
+current item.

package.yaml

@@ -4,7 +4,7 @@ license:             MIT
 author:              "Garmelon <joscha@plugh.de>"
 copyright:           "2020 Garmelon"
 
-synopsis:            A TUI viewer for GHC .prof files that can fold/unfold sections
+synopsis:            A TUI viewer for GHC .prof files
 description:         Please see the README on GitHub at <https://github.com/Garmelon/profold#readme>
 github:              "Garmelon/profold"