fix(om2): move mermaid diagram outside the spec

Currently it only renders correctly in github, not the website, so
we want to switch to pre-rendering into some picture that the markdown
can include. Preferably SVG.

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

Author: krajorama

docs/specs/om/open_metrics_spec_2_0.md

@@ -72,56 +72,6 @@ The word "RESERVED" is used in this document to designate values, names, or fiel
 
 This section MUST be read together with the ABNF section. In case of disagreements between the two, the ABNF's restrictions MUST take precedence.
 
-```mermaid
-classDiagram
-    class MetricSet
-    class MetricFamily
-    class MetricFamilyType {
-        <<enumeration>>
-        gauge
-        counter
-        stateset
-        info
-        histogram
-        gaugehistogram
-        summary
-        unknown
-    }
-    class Metric
-    class LabelSet
-    class Label
-    class Sample
-    class Timestamp
-    class Exemplar
-    class SampleValue {
-        <<abstract>>
-    }
-    class Number
-    class CompositeValue
-    class HistogramValue
-    class GaugeHistogramValue
-    class SummaryValue
-
-    MetricSet "1" --> "0..*" MetricFamily
-    MetricFamily "1" --> "1" MetricFamilyType : type
-    MetricFamily "1" --> "0..*" Metric
-    Metric "1" --> "1" LabelSet
-    Metric "1" --> "1..*" Sample
-    LabelSet "1" --> "0..*" Label
-    Sample --> "1" SampleValue : value
-    Sample --> "0..1" Timestamp : timestamp
-    Sample --> "0..1" Timestamp : start timestamp
-    Sample --> "0..*" Exemplar
-    SampleValue <|-- Number
-    SampleValue <|-- CompositeValue
-    CompositeValue <|-- HistogramValue
-    CompositeValue <|-- GaugeHistogramValue
-    CompositeValue <|-- SummaryValue
-    Exemplar --> "1" LabelSet
-    Exemplar --> "1" Number : value
-    Exemplar --> "1" Timestamp
-```
-
 ### Data Types
 
 #### Sample Values

public/assets/docs/specs/om/om2_data_model.mermaid

@@ -0,0 +1,49 @@
+```mermaid
+classDiagram
+    class MetricSet
+    class MetricFamily
+    class MetricFamilyType {
+        <<enumeration>>
+        gauge
+        counter
+        stateset
+        info
+        histogram
+        gaugehistogram
+        summary
+        unknown
+    }
+    class Metric
+    class LabelSet
+    class Label
+    class Sample
+    class Timestamp
+    class Exemplar
+    class SampleValue {
+        <<abstract>>
+    }
+    class Number
+    class CompositeValue
+    class HistogramValue
+    class GaugeHistogramValue
+    class SummaryValue
+
+    MetricSet "1" --> "0..*" MetricFamily
+    MetricFamily "1" --> "1" MetricFamilyType : type
+    MetricFamily "1" --> "0..*" Metric
+    Metric "1" --> "1" LabelSet
+    Metric "1" --> "1..*" Sample
+    LabelSet "1" --> "0..*" Label
+    Sample --> "1" SampleValue : value
+    Sample --> "0..1" Timestamp : timestamp
+    Sample --> "0..1" Timestamp : start timestamp
+    Sample --> "0..*" Exemplar
+    SampleValue <|-- Number
+    SampleValue <|-- CompositeValue
+    CompositeValue <|-- HistogramValue
+    CompositeValue <|-- GaugeHistogramValue
+    CompositeValue <|-- SummaryValue
+    Exemplar --> "1" LabelSet
+    Exemplar --> "1" Number : value
+    Exemplar --> "1" Timestamp
+```