Documentation: add special SVGs for dark mode (#3104)

Signed-off-by: Coline PILOQUET <coline.piloquet@rte-france.com>

docs/grid_exchange_formats/psse/import.md

@@ -165,7 +165,8 @@ The transformer is connected at both ends if the branch status (field `STAT` in
 
 In PSS®E the transformer model allows to define a ratio and angle at the end `1` and only a fixed ratio at the end `2`. The transformer magnetizing admittance is modeled between the bus and the ratio of the end `1`. The PowSyBl grid model supports a ratioTapChanger and a phaseTapChanger at the end `1` and the magnetizing admittance is between the ratio and the transmission impedance.
 
-![TwoWindingsTransformerModels](img/two-windings-transformer-model.svg){width="100%" align=center}
+![TwoWindingsTransformerModels](img/two-winding-transformer-model.svg){width="100%" align=center class="only-light"}
+![TwoWindingsTransformerModels](img/dark_mode/two-winding-transformer-model.svg){width="100%" align=center class="only-dark"}
 
 To express the PSS®E electric attributes of the transformer in the PowSyBl grid model the following conversions are performed:
 
@@ -218,7 +219,8 @@ When a three windings transformer is modeled the two windings transformer steps
 - Each winding can have a complex ratio and a `ratioTapChanger` or `phaseTapChanger` with its corresponding control, always at end `1`. The current PowSyBl version only supports one enabled control by three windings transformer so if there is more than one enabled only the first (winding `1`, winding `2`, winding `3`) is kept enabled, the rest are automatically disabled.
 - In three windings transformers the status attribute (field `STAT` in the _Transformer Data_ record) could be `0` that means all the windings disconnected, `1` for all windings connected, `2` for only the second winding disconnected, `3` for the third winding disconnected and `4` for the first winding disconnected.
 
-![ThreeWindingsTransformerModels](img/three-windings-transformer-model.svg){width="100%" align=center}
+![ThreeWindingsTransformerModels](img/three-winding-transformer-model.svg){width="100%" align=center class="only-light"}
+![ThreeWindingsTransformerModels](img/dark_mode/three-winding-transformer-model.svg){width="100%" align=center class="only-dark"}
 
 ### Slack bus
 

docs/grid_model/additional.md

@@ -85,7 +85,8 @@ The component on which the current limits are applied can safely remain
 between the preceding limit (it could be another temporary limit or a permanent limit) and this limit for a duration up to the acceptable duration.
 Please look at this scheme to fully understand the modelling (the following example shows current limits but this modelling is valid for all loading limits):
 
-![Loading limits model](img/currentLimits.svg){width="50%" align=center}
+![Loading limits model](img/current-limits.svg){width="50%" align=center class="only-light"}
+![Loading limits model](img/dark_mode/current-limits.svg){width="50%" align=center class="only-dark"}
 
 Note that, following this modelling, in general the last temporary limit (the higher one in value) should be infinite with an acceptable duration different from zero, except for tripping current modeling where the last temporary limit is infinite with an acceptable duration equal to zero. If temporary limits are modeled, the permanent limit becomes mandatory.
 
@@ -118,7 +119,8 @@ CurrentLimits currentLimits = network.getDanglingLine("DL").newCurrentLimits()
     .endTemporaryLimit()
     .add();
 ```
-![Current limits scheme_example1](img/currentLimitsExample1.svg)
+![Current limits scheme_example1](img/current-limits-example1.svg){align=center class="only-light"}
+![Current limits scheme_example1](img/dark_mode/current-limits-example1.svg){align=center class="only-dark"}
 
 ##### Second example
 This second example creates a `CurrentLimits` instance containing one permanent limit and three temporary limits, one of them having an infinite limit value.
@@ -142,7 +144,8 @@ CurrentLimits currentLimits = network.getDanglingLine("DL").newCurrentLimits()
     .endTemporaryLimit()
     .add();
 ```
-![Current limits scheme_example2](img/currentLimitsExample2.svg)
+![Current limits scheme_example2](img/current-limits-example2.svg){align=center class="only-light"}
+![Current limits scheme_example2](img/dark_mode/current-limits-example2.svg){align=center class="only-dark"}
 
 (phase-tap-changer)=
 ## Phase tap changer