dolt-add: add page (#5476)

pages/common/dolt-add.md

@@ -0,0 +1,12 @@
+# dolt add
+
+> Add the contents of a table to the list of Dolt staged tables.
+> More information: <https://github.com/dolthub/dolt>.
+
+- Add a table to the list of staged tables (stage a table):
+
+`dolt add {{table}}`
+
+- Stage all tables:
+
+`dolt add --all`