Documentation Revamp

Co-authored-by: jbdoumenjou <jb.doumenjou@gmail.com>

docs/content/providers/file.md

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+# TODO -- File
+
+Good Old Configuration File
+{: .subtitle } 
+
+## Configuration
+
+### Full Example in toml
+
+`TO COMPLETE`
+
+### In same file
+
+`TO COMPLETE`
+
+## In dedicated file
+
+`TO COMPLETE`
+
+### Old Content
+
+Traefik can hot-reload those rules which could be provided by multiple configuration backends.
+
+We only need to enable `watch` option to make Traefik watch configuration backend changes and generate its configuration automatically.
+Routes to services will be created and updated instantly at any changes.
+
+Please refer to the configuration backends section to get documentation on it.