Add readme

README.md

+Webservice
+==========
+
+A Go-based simple web service meant to be the subject for any tutorial
+or even the project work.
+
+
+__Prerequisites:__
+
+* Go toolchain (install via system package manager or [by hand](https://go.dev/doc/install))
+
+
+__Main interactions:__
+
+1. Install dependencies: `go get -t ./...`
+2. Run locally: `go run .`
+3. Execute unit tests: `go test -race -v ./...`
+4. Build artifact: `go build -o ./artifact.bin ./*.go`
+
+For more details, please refer to the `Makefile`.