doc: add documntation of Pulse and PixelPulse

- Everything from [SensorCharge](#sensorcharge)

- The associated [DepositedCharge](#depositedcharge) object

  ([`getDepositedCharge()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1propagatedcharge/#function-getdepositedcharge))

- The associated induced pulses, if any

- The associated induced [pulses](#pulse), if any

  ([`getPulses()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1propagatedcharge/#function-getpulses))

- The carrier state of the charge carriers described below

  ([`getState()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1propagatedcharge/#function-getstate))

- The associated time of the charge in local and global coordinates

  ([`getLocalTime()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelcharge/#function-getlocaltime),

   [`getGlobalTime()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelcharge/#function-getglobaltime))

- The recorded charge pulse, if any

- The recorded [charge pulse](#pulse), if any

  ([`getPulse()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelcharge/#function-getpulse))

For more details refer to the [code reference](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelcharge/).

## Pulse

The pulse object is a meta class mainly used to hold the time information of a charge pulse arriving at the collection

implant, if such information is available in the simulation. A pulse object always has a fixed time binning chosen during the

creation of the object. It inherits from [std::vector<doulbe>](https://en.cppreference.com/w/cpp/container/vector).

Main parameters:

- The total charge of the pulse

  ([`getCharge()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pulse/#function-getcharge))

- The time binning of the pulse

  ([`getBinning()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pulse/#function-getbinning))

For more details refer to the [code reference](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pulse/)

## PixelHit

The digitised pixel hits after processing the [PixelCharge](#pixelcharge) in the detector's front-end electronics. The object

  ([`getLocalTime()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelhit/#function-getlocaltime),

   [`getGlobalTime()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelhit/#function-getglobaltime))

For more details refer to the [code reference](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelhit/).

## PixelPulse

If the detector's front-end electronics provide a digitized front-end pulse, this object can be used to store that

information. It inherits from the [Pulse](#pulse) object.

Main parameters:

- Everything from [Pulse](#pulse)

- The pixel corresponding to the digitized pulse

  ([`getPixel()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelpulse/#function-getpixel))

  and its index

  ([`getIndex()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelpulse/#function-getindex))

- The corresponding [pixel charge](#pixelcharge)

  ([`getPixelCharge()`](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelpulse/#function-getpixelcharge))

For more details refer to the [code reference](https://allpix-squared.docs.cern.ch/reference/classes/classallpix_1_1pixelpulse/).

[@pdg]: http://hepdata.cedar.ac.uk/lbl/2016/reviews/rpp2016-rev-monte-carlo-numbering.pdf

[@ap2-doxygen]: https://allpix-squared.docs.cern.ch/reference/