add tutorial on delay estimation

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% :tada:

Comparison is base (2a41770) 86.62% compared to head (37a2304) 86.64%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #135 +/- ## ========================================== + Coverage 86.62% 86.64% +0.01% ========================================== Files 12 12 Lines 2243 2246 +3 ========================================== + Hits 1943 1946 +3 Misses 300 300 ``` | [Flag](https://app.codecov.io/gh/baggepinnen/ControlSystemIdentification.jl/pull/135/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Fredrik+Bagge+Carlson) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/baggepinnen/ControlSystemIdentification.jl/pull/135/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Fredrik+Bagge+Carlson) | `86.64% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Fredrik+Bagge+Carlson#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files Changed](https://app.codecov.io/gh/baggepinnen/ControlSystemIdentification.jl/pull/135?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Fredrik+Bagge+Carlson) | Coverage Δ | | |---|---|---| | [src/plotting.jl](https://app.codecov.io/gh/baggepinnen/ControlSystemIdentification.jl/pull/135?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Fredrik+Bagge+Carlson#diff-c3JjL3Bsb3R0aW5nLmps) | `92.52% <100.00%> (+0.07%)` | :arrow_up: |

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