metrics: now support TOML files (#3724)

* metrics: now support TOML files

* prettier

content/docs/command-reference/metrics/index.md

@@ -71,8 +71,8 @@ stages:
 
 ### Supported file formats
 
-Metrics can be organized as tree hierarchies in JSON or YAML 1.2 files. DVC
-addresses specific metrics by the tree path. In the JSON example below, five
+Metrics can be organized as tree hierarchies in JSON, TOML, or YAML 1.2 files.
+DVC addresses specific metrics by the tree path. In the JSON example below, five
 metrics are presented: `train.accuracy`, `train.loss`, `train.TN`, `train.FP`
 and `time_real`.
 

content/docs/command-reference/run.md

@@ -209,9 +209,9 @@ $ dvc run -n second_stage './another_script.sh $MYENVVAR'
 - `-m <path>`, `--metrics <path>` - specify a metrics file produced by this
   stage. This option behaves like `-o` but registers the file in a `metrics`
   field inside the `dvc.yaml` stage. Metrics are usually small, human readable
-  files (JSON or YAML) with scalar numbers or other simple information that
-  describes a model (or any other data artifact). See `dvc metrics` to learn
-  more about _metrics_.
+  files (JSON, TOML, or YAML) with scalar numbers or other simple information
+  that describes a model (or any other data artifact). See `dvc metrics` to
+  learn more about _metrics_.
 
 - `-M <path>`, `--metrics-no-cache <path>` - the same as `-m` except that DVC
   does not track the metrics file (same as with `-O` above). This means that

content/docs/command-reference/stage/add.md

@@ -204,9 +204,9 @@ data science experiments.
 - `-m <path>`, `--metrics <path>` - specify a metrics file produced by this
   stage. This option behaves like `-o` but registers the file in a `metrics`
   field inside the `dvc.yaml` stage. Metrics are usually small, human readable
-  files (JSON or YAML) with scalar numbers or other simple information that
-  describes a model (or any other data artifact). See `dvc metrics` to learn
-  more about _metrics_.
+  files (JSON, TOML, or YAML) with scalar numbers or other simple information
+  that describes a model (or any other data artifact). See `dvc metrics` to
+  learn more about _metrics_.
 
 - `-M <path>`, `--metrics-no-cache <path>` - the same as `-m` except that DVC
   does not track the metrics file (same as with `-O` above). This means that