docs(robotframework.md): add a chapter about faster development.

Addressed to #1021

[skip ci]

Author: php-coder

docs/robotframework.md

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+# Robot Framework
+
+## Faster Iterations
+
+As we already know, `./mvnw verify` runs all the integration tests. But let's
+suppose that we are working on a single test and we need to run it many times
+until it will work as desired. In this case, we would like to iterate faster
+and at least don't run all the tests, but the only one that we are working on.
+
+In this case we can (temporary) mark the test with a unique tag, let’s say
+`testme`, and ask `robotframework-maven-plugin` to execute only tests with such
+a tag:
+```console
+./mvnw verify -Dincludes=testme
+```
+
+Now we run much less tests but could we make the execution even faster? Sure,
+we can! Let's look on what exactly `./mvnw verify` does:
+1) it runs the application (this in turn includes many steps, like code
+   compilation, preparation of the resources, running unit tests and so on)
+2) it runs [Wiremock server](wiremock.md) that is required by some tests
+3) it executes the integration tests
+
+As we modify only one (or more) of the integration tests, we don't need to
+re-run the whole application every time. Also, if our test doesn't use
+Wiremock, we might also skip this part entirely. To do so, we should manually
+execute all the steps that we need:
+
+1) run the application:
+   ```console
+   ./mvnw spring-boot:run`
+   ```
+2) in another terminal, run Wiremock server, only if your test need it:
+   ```console
+   ./mvnw wiremock:run -DkeepRunning=true`
+   ```
+3) in another terminal, run integration tests as many times as you need:
+   ```console
+   ./mwnw robotframework:run -Dincludes=testme`
+   ```
+