Update docs

docs/developer/guide.md

@@ -1,11 +1,48 @@
 # Developer guide
 
-## Docs
+## Running tests
 
-See `docs/` folder in the repository.
+```
+git clone https://github.com/kdheepak/taskwarrior-tui
+cd taskwarrior-tui
+
+git clone github.com/kdheepak/taskwarrior-testdata tests/data
+source .env
+
+cargo test
+```
+
+## Running debug build
+
+```
+cargo run
+```
+
+## Running release build
+
+```
+cargo run --release
+```
+
+## Testing individual function
+
+If you want to test the `test_taskwarrior_timing` function in `src/app.rs`:
+
+```
+cargo test -- app::tests::test_taskwarrior_timing --nocapture
+```
+
+## Contributing to documentation
+
+See `docs/` folder in the repository: <https://github.com/kdheepak/taskwarrior-tui>
+
+When you make a PR to the repository, a preview of the documentation is rendered and a link is posted to the PR.
 
 ## Internals of `taskwarrior-tui`
 
-<!-- TODO -->
-
 `taskwarrior-tui` is a state driven terminal user interface.
+Keyboard events are read asynchronously and is communicated using channels.
+Most of the logic is implemented in `src/app.rs`.
+The difference between the previous state and the current state of the TUI is rendered every `Tick` by `tui-rs`.
+`app.draw_...` functions are responsible for rendering the UI.
+Actions for key presses are taken in [`app.handle_input(&mut self, input: Key)`](https://github.com/kdheepak/taskwarrior-tui/blob/f7f89cbff180f81a3b27112d676d6101b0b552d8/src/app.rs#L1893).

mkdocs.yml

@@ -49,5 +49,5 @@ nav:
     - Key configuration:    configuration/keys.md
     - Color configuration:  configuration/colors.md
     - Advanced:             configuration/advanced.md
-  # - Developer Guide:
-  #   - Guide:                developer/guide.md
+  - Developer Guide:
+    - Guide:                developer/guide.md