Enhanced Developer Documentation. Docker Setup and Readability Improvements (#10)

👀 
I noticed that the developer documentation section lacked explicit
instructions on setting up **Docker**, a crucial step for running unit
tests and ensuring a seamless development environment. Recognizing the
importance of this step for new and existing developers, I have added
Docker setup instructions to the "Precondition" section of the README.

🆙 💅🏻 
In addition to integrating Docker setup instructions, I took the
opportunity to improve the overall readability of the README file. These
improvements include better formatting, clearer descriptions of commands
and modules, and a more organized presentation of content. This should
make the documentation more **accessible and easier** to follow,
especially for developers who are new to the project.

Co-authored-by: haskiindahouse <>

Author: haskiindahouse

docs/developer.md

@@ -1,28 +1,51 @@
 
 # Developer Docs
 
-* Running all unit tests: `./mill -i -w "__.test"`. 
+## Precondition
+Before running the unit tests, ensure the following steps are completed:
 
-* Running all unit tests on one database: `./mill -i -w "__.test scalasql.sqlite"`. This
+1. **Start Docker on Your Machine:**
+   Ensure that Docker is running. You can verify this by executing `docker info` in your terminal. If Docker is not running, start it using your system's preferred method (e.g., using the Docker desktop application or by running `systemctl start docker` on Linux).
+
+## Running Unit Tests
+To facilitate efficient testing, you can choose from several commands based on your testing needs:
+
+### Run all Tests
+* Running all unit tests: 
+  ```bash
+    ./mill -i -w "__.test"
+  ```
+
+### Quick Database-Specific Tests
+* Running all unit tests on one database. This
   is much faster than running all tests, and useful for quick iteration for changes that
-  are not database specific.
+  are not database specific:
+  ```bash
+  ./mill -i -w "__.test scalasql.sqlite"
+  ```
 
-* Re-generating docs: `./mill -i "__.test" + generateTutorial + generateReference`
+### Full Test Suite with Documentation Generation
+* Re-generating docs:
+  ```bash
+  ./mill -i "__.test" + generateTutorial + generateReference
+  ```
     * Note that ScalaSql's reference docs are extracted from the test suite, and thus we need
       to make sure to run the test suite before re-generating them.
 
+### Code Formatting and Auto-Fixes
 * Fix all auto-generating and auto-formatting issues at once via
-```
-./mill -i -w __.fix + mill.scalalib.scalafmt.ScalafmtModule/reformatAll __.sources + "scalasql[2.13.12].test" + generateTutorial + generateReference
-```
+  ```bash
+  ./mill -i -w __.fix + mill.scalalib.scalafmt.ScalafmtModule/reformatAll __.sources + "scalasql[2.13.12].test" + generateTutorial + generateReference
+  ```
 
+## Benchmarking
 * You can run ad-hoc benchmarks using any test case via the `SCALASQL_RUN_BENCHMARK` 
-  environment variable, e.g.
-
-```
-SCALASQL_RUN_BENCHMARK=5000 ./mill -i -w __.test scalasql.sqlite.SubQueryTests.deeplyNested
-```
+environment variable, e.g.
+    ```bash
+    SCALASQL_RUN_BENCHMARK=5000 ./mill -i -w __.test scalasql.sqlite.SubQueryTests.deeplyNested
+    ```
 
+## ScalaSql Modules Overview
 * ScalaSql comprises 4 main submodules:
     * `scalasql.core`: the core functionality of evaluating `SqlStr` queries, but without any typed
       helpers to construct them