Refine github extension keys

[stain]

The github extension is only explained by example.

The two keys github_repository and github_URI are not explained and seem to be partially overlapping. The camel_Case is also inconsistent.

Given that these are URLs I think the extension should support any source control repository, not just github.com, perhaps something like:

"extension_domain":{
  "scm_extension": {
    "scm_repository": "https://github.com/example/repo1",
    "scm_type": "git",
    "scm_branch": "c9ffea0b60fa3bcf8e138af7c99ca141a6b8fb21",
    "scm_path": "workflow/hive-viral-mutation-detection.cwl",
    "scm_preview": "https://github.com/example/repo1/blob/c9ffea0b60fa3bcf8e138af7c99ca141a6b8fb21/workflow/hive-viral-mutation-detection.cwl"
}

Here's how Maven defines it's scm metadata.

[stain]

Marked as discuss - we can keep this simple or general (or something in-between)

[mr-c]

I agree, we shouldn't bake in a commercial third party into the BCO spec/standard

[mr-c]

Thanks for clarifying, @HadleyKing but I think the example should be updated to match Stian's suggestion.

[HadleyKing]

github_extension to scm_extension

• user_guide.md:520: "github_extension": {

• extension-github.md:9: "github_extension": {

• antiviral_resistance_detectionTypeDef.json:23: "github_extension": {

• HCV1a.json:91: "github_extension": {

• bco-domains.md:22: "github_extension": {

• README.md:46: * GitHub extension

• bco-domains.md:74:* GitHub extension