doc(license): put license files

[kachick]

Resolves #16
Resolves #3

I think we often confuse because GitHub does not display the license here.

I believe this repository is licensed under Apache-2.0, because of written in

vscode-kdl/package.json

Line 6 in 646d7b8

"license": "Apache-2.0",

So copied files from kdl-org/kdl-rs#87 with project name changes in NOTICE file

Checked the result with licensee 9.18.0

Before

License:        Apache-2.0
Matched files:  package.json
package.json:
  Confidence:  90.00%
  Matcher:     Licensee::Matchers::NpmBower
  License:     Apache-2.0

After

License:        Apache-2.0
Matched files:  LICENSE, package.json
LICENSE:
  Content hash:  bec905d850e7f5dc2e2db78a950d4a9db560a0b8
  Confidence:    100.00%
  Matcher:       Licensee::Matchers::Exact
  License:       Apache-2.0
package.json:
  Confidence:  90.00%
  Matcher:     Licensee::Matchers::NpmBower
  License:     Apache-2.0

Motivation of these PRs

I have a PR for micro-editor as zyedidia/micro#3549 from https://github.com/kachick/micro-kdl
So I want to clarify I can refer these implementations 🙏

[zkat]

yep, thanks :)

[kachick]

Thank you!