Add: show examples on hover.

[yassun7010]

What does this PR do?

If "examples" is defined in the schema, display it on the hover.

I think it useful to show what kind of input is expected for a string in user format.

Is it tested? How?

A test was added.

[evidolob]

@yassun4dev We have test failing on this PR.
Also could you fix sign of the commit, it seems that you use two accounts.

[yassun7010]

@evidolob Oh, sorry...

I fixed sign of the commit, and check why the test failed on Linux only.
Try again CI, the pipeline was successful.

[coveralls]

Coverage increased (+0.2%) to 81.356% when pulling a58c82f on yassun4dev:add_examples_hover into 2f34acf on redhat-developer:main.

[gorkem]

@yassun4dev Are there any JSON schemas that you can suggest for testing this functionality?

[yassun7010]

@gorkem I added one test case and put a simple schema in it.

You need more comprehensive testing as separate schema files?

[gorkem]

Not necessarily for testing but wanted to see real world usages.

[yassun7010]

@gorkem I see.

I have encountered some cases that require examples in real world.

1. It is too complicated to describe with 'pattern', and 'examples' assists the reading.

{
  "type": "object",
  "properties": {
    "range": {
      "type": "string",
      "description": "Sheet range of Excel.",
      "pattern": "^[A-Z]+[1-9][0-9]*:[A-Z]+[1-9][0-9]*$", // It's too complicated pattern.
      "examples": ["A1:B12"] // Easy to read and understand. 
    }
  }
}

2. Since the exception data already exists, "enum" and "pattern" cannot be used, but a recommended hint is needed.

[gorkem]

Thanks for the contribution. Just one comment on the format of the hover. It is up-to you if you want to address it or not.

[gorkem]

Not a big one but I am not sure if we need the [ in here. The hovers looked better for me without them

[yassun7010]

@gorkem I fixed hover format. I think it looks better. Thank you!!