feat: add json schema validation with ajv

[ANGkeith]

fixes #859

Main motivation is that the ajv will make gitlab-ci-local less likely to produce false positive

[ANGkeith]

i don't know how to use import here

[ANGkeith]

currently only dumping out the yaml...

can't really find a nice way to parse the validate.errors that catches all scenarios

[firecow]

I'm pretty sure I saw a way to pretty print AJV errors somewhere, let me dig around.

[ANGkeith]

MR should be ready now. the ajv will be a second layer check...

Main motivation is that the ajv will make gitlab-ci-local less likely to produce false positive

Given the following gitlab-ci.yml input:

default:
  tags:
    - 1

foo:
  image: bash
  script:
    - echo

Using fallback branch data
parsing and downloads finished in 28 ms
Invalid gitlab-ci configuration! It have failed the json schema validation. Dump the following to the pipeline editor to debug:
    stages:
  - .pre
  - build
  - test
  - deploy
  - .post
default:
  tags:
    - 1
foo:
  image:
    name: bash
  script:
    - echo

NOTE: This is beta feature, which can be disabled with `gitlab-ci-local --enable-json-schema-validation=false`

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.4% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[firecow]

@ANGkeith I've approved, I'll test and publish a new version tomorrow, if you have merged this by then.