add diagram for pv simple and nwp_pv datapipeline

Author: peterdudfield

ocf_datapipes/training/nwp_pv.md

@@ -0,0 +1,29 @@
+# NWP PV 
+
+nwp_pv.py is a training pipeline for loading NWP and PV data. 
+
+The location is chosen using the PV data, PV and NWP location data is made. 
+Then a time is chosen, and PV and NWP examples are made. 
+These examples are then made into batches and put together into one Batch. 
+
+```mermaid
+  graph TD;
+      A([Load PV data])-->B;
+      B[Choose location]-->C;
+      A1([Load NWP data])-->B2;
+      A-->B1;
+      B-->C1
+      B1[Filter]-->C;
+      B2[Filter]-->C1;
+      C[Location PV data]-->E;
+      C1[Location NWP data];
+      C-->D[Choose time]-->E;
+      C1-->D;
+      D-->E1;
+      C1-->E1;
+      E[PV example]-->F;
+      E1[NWP example]-->F1;
+      F[PV batch] --> G;
+      F1[NWP batch] --> G;
+      G[Batch];
+```

ocf_datapipes/training/simple_pv.md

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+# Simple PV 
+
+simple_pv.py has a training pipeline for just loading PV data. 
+
+The location is chosen using the PV data, PV location data is made. 
+Then a time is chosen, and PV examples are made. 
+These examples are then made into batches.  
+
+```mermaid
+  graph TD;
+      A([Load PV data])-->B;
+      A-->B1;
+      B1[Filter]-->C;
+      B[Choose location]-->C;
+      C[Location PV data]-->E;
+      C-->D[Choose time]-->E;
+      E[PV example]-->F;
+      F[PV batch];
+```