Many changes regarding Json support and memory improvement

- Support for ArduinoJson 7
- Fixed missing `float step` for slider when using short ranges or big ranges
- Supports WebSocket batching to avoid crash with the initial layout sending. Batch sizes can be controlled with `DASH_JSON_SIZE`.
- Mitigate concurrency issue with `isAsyncAccessInProgress()` to avoid updating cards while the layout is being generated
- Added `DASH_DEBUG` to show WS frames information
- Changed card and stat names to `const char*` to improve memory usage. This makes them immutable and require to use constants.
- Removed the ability to change a stat name (for this dynamic use case we can remove and recreate a stat)
- refreshLayout() refactoring in order to avoid too many layout refresh requests when updating components dynamically: let the caller trigger a layout refresh once.
- Removed refreshStatistics() because it it not refreshing the stats only but all the updated cards also
- Removed update calls when adding / removing cards and stats in order to avoid trigger a sequence of full layout updates: this is u to the user to call refreshLayout() when he has finished

.gitignore

@@ -34,7 +34,8 @@
 
 node_modules
 .DS_Store
-.vscode
+/.vscode/*
+!/.vscode/settings.json
 ./vue-frontend/dist
 /build
 /portal

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "C_Cpp.clang_format_fallbackStyle": "{ BasedOnStyle: LLVM, UseTab: Never, IndentWidth: 2, TabWidth: 2, AllowShortIfStatementsOnASingleLine: false, IndentCaseLabels: true, ColumnLimit: 0, AccessModifierOffset: -2, NamespaceIndentation: All, FixNamespaceComments: false, IndentAccessModifiers: true, PointerAlignment: Left, ReferenceAlignment: Left, ContinuationIndentWidth: 2}"
+}

src/Card.cpp

@@ -3,14 +3,15 @@
 /*
   Constructor
 */
-Card::Card(ESPDash *dashboard, const int type, const char* name, const char* symbol, const int min, const int max){
+Card::Card(ESPDash *dashboard, const int type, const char* name, const char* symbol, const int min, const int max, const float step){
   _dashboard = dashboard;
   _id = dashboard->nextId();
   _type = type;
   _name = name;
   _symbol = symbol;
   _value_min = min;
   _value_max = max;
+  _value_step = step;
   _dashboard->add(this);
 }
 

src/Card.h

@@ -33,7 +33,7 @@ class Card {
     ESPDash *_dashboard;
 
     uint32_t _id;
-    String _name;
+    const char* _name;
     int   _type;
     bool  _changed;
     enum { INTEGER, FLOAT, STRING } _value_type;
@@ -44,11 +44,12 @@ class Card {
     String _value_s;
     int _value_min;
     int _value_max;
+    float _value_step;
     String _symbol;
     std::function<void(int value)> _callback = nullptr;
 
   public:
-    Card(ESPDash *dashboard, const int type, const char* name, const char* symbol = "", const int min = 0, const int max = 0);
+    Card(ESPDash *dashboard, const int type, const char* name, const char* symbol = "", const int min = 0, const int max = 0, const float step = 1);
     void attachCallback(std::function<void(int)> cb);
     void update(int value);
     void update(int value, const char* symbol);

src/Chart.h

@@ -33,7 +33,7 @@ class Chart {
     ESPDash *_dashboard;
 
     uint32_t _id;
-    String _name;
+    const char *_name;
     int   _type;
     bool  _changed;
     GraphAxisType _x_axis_type;