mkvmerge: add page (#5943)

pages/common/mkvmerge.md

@@ -0,0 +1,16 @@
+# mkvmerge
+
+> Merge and extract multimedia streams.
+> More information: <https://mkvtoolnix.download/doc/mkvmerge.html>.
+
+- Display information about a Matroska file:
+
+`mkvmerge --identify {{path/to/file.mkv}}`
+
+- Extract the audio from track 1 of a specific file:
+
+`mkvextract tracks {{path/to/file.mkv}} {{1}}:{{path/to/output.webm}}`
+
+- Extract the subtitle from track 3 of a specific file:
+
+`mkvextract tracks {{path/to/file.mkv}} {{3}}:{{path/to/subs.srt}}`