[Feature] support go install-based installation

[orpheuslummis]

Is your feature request related to a problem? Please describe.
New standard in Go is to be able to install executables directly with go install

Describe the solution you'd like

• go install https://github.com/ekalinin/github-markdown-toc.go ...
• update README in light of it

[KEINOS]

Since gh-md-toc is already compatible with go.mod, the go install must include the main package path in /cmd/gh-md-toc and the version of the application being followed.

The below command worked for me. (GO version go1.19 linux/amd64)

go install github.com/ekalinin/github-markdown-toc.go/cmd/gh-md-toc@latest

For reproducibility here's the sample on Docker.

$ docker run --rm -it golang:alpine /bin/sh
/go # cd

~ # go install github.com/ekalinin/github-markdown-toc.go/cmd/gh-md-toc@latest
go: downloading gopkg.in/alecthomas/kingpin.v2 v2.2.4
go: downloading github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc
go: downloading github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf

~ # gh-md-toc --version
1.2.0

~ # go version
go version go1.19 linux/amd64

• Ref: Compile and install packages and dependencies | go command @ pkg.go.dev

[KEINOS]

@orpheuslummis

Nothing is better than a better document. I pull-requested how to go install in the README.md @ PR #37.

[KEINOS]

@orpheuslummis

The PR #37 has been merged! 🎉 If this fits your needs, please close the issue. 👍

[orpheuslummis]

great. thank you @KEINOS !