doc(readme): added readme file

README.md

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+# Go Notes example
+
+### Tech stack:
+
+* [GRPC Gateway](https://github.com/grpc-ecosystem/grpc-gateway) - gRPC Gateway
+* [GRPC](https://grpc.io/) - gRPC
+* [Protobuf](https://developers.google.com/protocol-buffers) - Protobuf
+* [Wire](https://github.com/google/wire) - Automated Initialization in Go
+* [SQLC](https://github.com/kyleconroy/sqlc) - A SQL Compiler
+* [Go-redis](https://github.com/go-redis/redis) - Redis client for Golang
+* [Zap](https://github.com/uber-go/zap) - Logger
+---
+
+* [Docker](https://www.docker.com/) - Docker
+* [Docer Compose](https://docs.docker.com/compose/) - Docker Compose
+* [Helm](https://helm.sh/) - Helm
+* [k8s](https://kubernetes.io/) - k8s
+* [GitHub Actions](https://github.com/features/actions) - GitHub Actions (_for lint and unit tests_)
+---
+
+* [Postman Collection](https://www.postman.com/) - Postman Collection (_third_party/PostmanCollection_)
+* [OpenAPI](https://swagger.io/specification/) - OpenAPI (_third_party/OpenAPI_)
+---
+
+* [Excalidraw](https://excalidraw.com) - Excalidraw for diagrams
+
+![go-notes.svg](doc/go-notes.svg)
+
+---
+
+### Usage local:
+
+```bash
+make docker-up   // run all containers with application
+```
+
+The service is available at http://localhost:5555/v1/api. You can check it using Postman by importing the collection
+located at `third_party/PostmanCollection/Notes.postman_collection.json`.
+
+### Stop containers:
+
+```bash
+make docker-down      // stop containers
+```
+
+---
+
+### TESTS
+
+### 1. Postman
+
+To import a collection into Postman, you should use the `Import` button in the top-left corner of the Postman window.
+
+Before running the tests, it's necessary to set the required environment variables:
+
+`baseUrl`: the address of the server where the project is running.
+
+Example: `http://localhost:5555/v1/api`
+
+To run the tests in Postman, you should select the collection (`Notes -> Tests`), and then click the
+button (`Run folder -> Run Notes`).
+
+The passed tests will appear as follows:
+
+![postman_tests.png](doc/postman_tests.png)
+
+---
+
+### Unit tests
+
+```bash
+make test-run   // run unit tests
+```
+
+---
+
+## k8s
+
+To deploy the project in Kubernetes (k8s), Helm is used.
+
+```bash
+cd .charts/go-notes/proxy && \
+helm dependency update && \
+helm install -f values.yaml go-notes .
+```
+
+---
+
+### Checking the Swagger documentation:
+
+Take the generated file `{{service}}.swagger.json` from the `third_party/OpenAPI` directory.
+Paste it into the [Swagger Editor](https://editor.swagger.io).
+
+![open_api.png](doc/open_api.png)