V1 api

[arl]

We will increase the major version number to v1 after this pull-request gets merged.

API changes:

• do not use global state (global variables) anymore.
• everything is based off a statsviz.Endpoint structure that users must instantiate, via statsviz.NewEndpoint()

TODO:

• [x] new API (based on statsviz.Endpoint)
• [ ] update doc
• [x] update examples
• [ ] expose API for the user to add their own plots

[codecov[bot]]

Codecov Report

Attention: 59 lines in your changes are missing coverage. Please review.

Comparison is base (cca6221) 90.00% compared to head (50ca4bc) 63.15%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #103 +/- ## =========================================== - Coverage 90.00% 63.15% -26.85% =========================================== Files 3 2 -1 Lines 90 171 +81 =========================================== + Hits 81 108 +27 - Misses 6 60 +54 Partials 3 3 ``` | [Files](https://app.codecov.io/gh/arl/statsviz/pull/103?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Aur%C3%A9lien+Rainone) | Coverage Δ | | |---|---|---| | [statsviz.go](https://app.codecov.io/gh/arl/statsviz/pull/103?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Aur%C3%A9lien+Rainone#diff-c3RhdHN2aXouZ28=) | `78.86% <79.62%> (+10.67%)` | :arrow_up: | | [userplot.go](https://app.codecov.io/gh/arl/statsviz/pull/103?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Aur%C3%A9lien+Rainone#diff-dXNlcnBsb3QuZ28=) | `22.91% <22.91%> (ø)` | |

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