chore: add python docs

docs/python.md

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+# Introduction
+
+> [!NOTE]
+> The following is valid as of 2024-03-18. Future versions of `jsii` might provide a more Pythonic approach.
+
+Using the python version of this package requires some extra steps to ensure everything works as expected.
+This document highlights only those steps, so for the basics, please refer to the [main README](../README.md), the [API docs](../API.md) and the [Typescript docs](typescript.md).
+
+## How to implement interfaces
+
+Since this package is written in Typescript and then exported to Python via `jsii`, using interfaces to pass props is not as straightforward as it should be.
+
+Whereas in Typescript you can simply pass the props like this:
+
+```ts
+const costMonitoring = new ApplicationCostMonitoring(
+    monitoringStack,
+    // ⬇︎⬇︎⬇︎ The props ⬇︎⬇︎⬇︎
+    {
+        applicationName: "my-application",
+        monthlyBudget: 200,want)
+        otherStacksIncludedInBudget: [secondStack, firstStack],
+        subscribers: ["[email protected]"],
+    }
+);
+```
+
+In python it is not so simple.
+
+The correct, and ONLY working approach is to:
+
+1. Create a new class (no inheritance)
+2. Decorate it with `@jsii.implements(<IMyInterface>)`
+3. Use getters and setters to define properties
+
+Example:
+
+```py
+import jsii
+
+from cost_monitoring_construct import IApplicationCostMonitoringProps
+
+@jsii.implements(IApplicationCostMonitoringProps)
+class CostMonitoringProps:
+    def __init__(self, props: dict[str, Any]) -> None:
+        self.props = props
+
+
+    @property
+    def application_name(self):
+        return self.props["application_name"]
+
+    @application_name.setter
+    def application_name(self, value: str):
+        self.props["application_name"] = value
+
+    @property
+    def default_topic(self):
+        return self.props.get("default_topic")
+
+    @default_topic.setter
+    def default_topic(self, value: str | None):
+        self.props["default_topic"] = value
+
+    # etc...
+```
+
+Later you can use this class directly in the `ApplicationCostMonitoring`:
+
+```py
+cost_monitoring = ApplicationCostMonitoring(
+    stack_to_monitor,
+    props=CostMonitoringProps(
+        {
+            "application_name": "my_app",
+            "monthly_limit_in_dollars": 100,
+            "subscribers": ["[email protected]"]
+        }
+    )
+)
+```
+
+## Sources and additional info
+
+- <https://aws.github.io/jsii/user-guides/lib-user/language-specific/python/>
+- <https://github.com/aws/jsii/issues/1027>