chore: release 0.3.0

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sqlness"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2021"
 authors = [
     "CeresDB Authors <ceresdbservice@gmail.com>",

README.md

@@ -19,7 +19,7 @@ $ tree examples/
 examples/
 ├── basic-case               # Testcase root directory
 │   └── simple               # One environment
-│       ├── config.toml      # Config file for current environment
+│       ├── config.toml      # Config file for current environment, optional
 │       ├── select.result    # Output result file
 │       └── select.sql       # Input SQL testcase
 ├── basic.rs                 # Entrypoint of this example
@@ -42,6 +42,11 @@ Usually `result` files should be tracked in git, whenever there are failed tests
 1. Update `result` to latest version(e.g. `git add`) if the newer result is right, or
 2. Restore `result` back to original version (e.g. `git checkout`), troubleshoot bugs in database implementation, and run tests again
 
+Flowchart below illustrates the typical steps when write a test.
+<p align="center">
+  <img src="sqlness-flowchart.svg" />
+</p>
+
 Below is the output of this example:
 ```bash
 Run testcase...