Publish convert command and add new documentation page (#700)

This PR publishes the new subcommand `convert`, and adds a new
documentation page.

This must be merged before the v0.10.0 release.

---------

Co-authored-by: Andrew Farries <andyrb@gmail.com>

Author: kvch

cmd/convert.go

@@ -24,7 +24,6 @@ func convertCmd() *cobra.Command {
 		Long:      "Convert SQL statements to a pgroll migration. The command can read SQL statements from stdin or a file",
 		Args:      cobra.MaximumNArgs(1),
 		ValidArgs: []string{"migration-file"},
-		Hidden:    true,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			reader, err := openSQLReader(args)
 			if err != nil {

docs/cli/convert.mdx

@@ -0,0 +1,24 @@
+---
+title: Convert
+description: Convert SQL migration files to a pgroll migration
+---
+
+## Command
+
+```
+$ pgroll convert --name 01_create_first_table /path/to/migration.sql
+```
+
+This reads the SQL statements from `/path/to/migration.sql` and translates them into a `pgroll` migration. The name of the migration will be `01_create_first_table`.
+
+### Read SQL statements from stdin
+
+If a file name is not specified `pgroll convert` reads the SQL statements from stdin.
+
+```
+$ cat 'CREATE TABLE my_table(name text);' | pgroll convert --name 01_create_first_table
+```
+
+<Warning>
+The generated pgroll migrations might include `up` and `down` migrations. Those must be filled in manually because currently `pgroll` is unable to infer correct up and down migrations.
+</Warning>