docs: update README

Closes #TNTP-3736

Author: patapenka-alexey

Makefile

@@ -33,3 +33,11 @@ coveralls-deps:
 	@echo "Installing coveralls"
 	@go get github.com/mattn/goveralls
 	@go install github.com/mattn/goveralls
+
+.PHONY: godoc_run
+godoc_run:
+	godoc -http=:6060
+
+.PHONY: godoc_open
+godoc_open:
+	xdg-open http://localhost:6060/pkg/$(shell go list -f "{{.ImportPath}}")

README.md

@@ -10,6 +10,27 @@
 
 # go-option: library to work with optional types
 
+Package `option` implements effective and useful instruments to work
+with optional types in Go. It eliminates code doubling and provides
+high performance due to:
+  - no memory allocations
+  - serialization without reflection (at least for pre-generated types)
+  - support for basic and custom types
+
+## Table of contents
+
+* [Pre-generated basic optional types](#pre-generated-basic-optional-types)
+* [Gentype Utility](#gentype-utility)
+* [Overview](#overview)
+* [Features](#features)
+* [Installation](#installation)
+* [Documentation](#documentation)
+* [Quick start](#quick-start)
+* [Generating Optional Types](#generating-optional-types)
+* [Using Generated Types](#using-generated-types)
+* [Run tests](#run-tests)
+* [Development](#development)
+
 ## Pre-generated basic optional types
 
 ## Gentype Utility
@@ -45,9 +66,24 @@ go install github.com/tarantool/go-option/cmd/gentypes@latest
 go get -tool github.com/tarantool/go-option/cmd/gentypes@latest
 ```
 
-### Usage
+## Documentation
+
+You could run the `godoc` server on `localhost:6060` with the command:
+
+```shell
+make godoc_run
+```
+
+And open the generated documentation in another terminal or use the
+[link][godoc-url]:
+
+```shell
+make godoc_open
+```
+
+## Quick start
 
-#### Generating Optional Types
+### Generating Optional Types
 
 To generate optional types for existing types in a package:
 
@@ -71,7 +107,7 @@ Flags:
    -128 and 127, no default value)
  • `-verbose`: Enable verbose output (default: `false`)
 
-#### Using Generated Types
+### Using Generated Types
 
 Generated types follow the pattern Optional<TypeName> and provide methods for working
 with optional values:
@@ -93,6 +129,27 @@ value := opt.UnwrapOr("default")
 err := opt.EncodeMsgpack(encoder)
 ```
 
+## Run tests
+
+To run default set of tests:
+
+```shell
+go test ./... -count=1
+```
+
+## Development
+
+You could use our Makefile targets:
+
+```shell
+make codespell
+make test
+make testrace
+make coveralls-deps
+make coveralls
+make coverage
+```
+
 [godoc-badge]: https://pkg.go.dev/badge/github.com/tarantool/go-option.svg
 [godoc-url]: https://pkg.go.dev/github.com/tarantool/go-option
 [actions-badge]: https://github.com/tarantool/go-option/actions/workflows/testing.yaml/badge.svg