(docs) get started

[lazarusA]

This PR adds:

• a new section get started with minimal jargon and explicit usage, hopefully is straightforward.
• a CHANGELOG.md file so that we can minimally document solved issues or new features
• a CONTRIBUTING.md file to encourage contributions from new users, for now consider it a minimal template.
• some features on the landing page
• moved files into different folders and re-arranged the menu into different topics, some are commented out since they are there now as place holders for new additions.

closes #248 #249 #250 #251 😄

[coveralls]

Pull Request Test Coverage Report for Build 23116724268

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.336%

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Totals
Change from base Build 23072019189:	0.0%
Covered Lines:	1403
Relevant Lines:	1704

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💛 - Coveralls

[lazarusA]

while creating the groups example,

using Zarr

store = Zarr.DirectoryStore("experiment.zarr")
g = zgroup(store, "", Zarr.ZarrFormat(3))

zcreate(Float64, g, "temperature", 100, 100; chunks=(50, 50), fill_value=0.0)
zcreate(Float64, g, "precipitation", 100, 100; chunks=(50, 50), fill_value=0.0)
g

I noticed that if we don't explicitly say zarr_format=3 in zcreate then it defaults to .zarray and .zattrs. I think the version should be inherit from g.

[mkitti]

Create an issue if you can, please.

[lazarusA]

Already done #247 😬

[lazarusA]

I will merge this.
There are not real changes to original docs, only the addition of get started which starts putting things into a more organise form.