feat: Add forecast

[mbauchet]

Description
Adding a forecast line to LineChart (and AreaChart).
New properties:

• forecastCategories that works like categories but for the forecast datas (Allows different label than default datas). It can also have multiple forecast lines for one data by passing an array of categories

  forecastCategories: ["Sales Forecast", "Successful Payments Forecast"] //for single forecast line by category

  forecastCategories: [["Sales Forecast Max", "Sales Forecast Min"], ["Successful Payments Forecast Max", "Successful Payments Forecast Min"]] //for two forecast lines by category

• forecastLineStyle that allow you to change the style for the forecast line (solid, dashed, dotted)

Related issue(s)
#572

What kind of change does this PR introduce? (check at least one)

• Bug fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

How has This been tested?
Using StoryBook

Screenshots (if appropriate):

The PR fulfills these requirements:

• It's submitted to the main branch
• When resolving a specific issue, it's referenced in the related issue section above
• My change requires a change to the documentation. (Managed by Tremor Team)
• I have added tests to cover my changes
• Check the "Allow edits from maintainers" option while creating your PR.
• Add refs #XXX or fixes #XXX to the related issue section if your PR refers to or fixes an issue.

[gondar00]

@severinlandolt any plans of adding this into the coming releases?

[nextjs-tsadei]

Any update on this PR? ANy plan to merge ?

[alexbalonperin]

I believe that you can write the above code (from line 29) as follows:

const objectsWithCategories = data.reduce((count, obj) => 
  count + categories.flat().some(c => obj.hasOwnProperty(c) && obj[c] !== null && obj[c] !== undefined), 
  0
)

[alexbalonperin]

Could you explain why you are adding 1 here? Maybe I am missing something obvious but it looks incorrect? 🤔