Add CSV Import documentation

Document importing of CSVs with format information and sample data

changelogs/unreleased/49231-import-issues-csv.yml

+---
+title: Add importing of issues from CSV file
+merge_request: 23532
+author:
+type: added

doc/user/project/issues/csv_import.md

+# Importing Issues from CSV
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23532) in GitLab 11.7.
+
+Issues can be imported by uploading a CSV file. The file will be processed in the background and a notification email
+will be sent to you once the import is completed.
+
+> **Note:** A permission level of `Developer` or higher is required to import issues.
+
+## CSV File Format
+
+### Header row
+
+CSV files must contain a header row with at least two columns: `title` and `description`, in that order.
+
+### Column separator
+
+The column separator is automatically detected from the header row.
+
+Supported separator characters are: commas (`,`), semicolons (`;`), and tabs (`\t`).
+
+### Row separator
+
+Lines ending in either `CRLF` or `LF` are supported.
+
+### Quote character
+
+The double-quote (`"`) character is used to quote fields so you can use the column separator within a field. To insert
+a double-quote (`"`) within a quoted field, use two double-quote characters in succession, i.e. `""`.
+
+### Data rows
+
+After the header row, succeeding rows must follow the same column order. The issue title is required while the
+description is optional.
+
+The user uploading the CSV file will be set as the author of the imported issues.
+
+## Sample Data
+
+```csv
+title,description
+My Issue Title,My Issue Description
+Another Title,"A description, with a comma"
+"One More Title","One More Description"
+```

doc/user/project/issues/index.md

@@ -142,6 +142,15 @@ to find out more about this feature.
 With [GitLab Starter](https://about.gitlab.com/pricing/), you can also
 create various boards per project with [Multiple Issue Boards](https://docs.gitlab.com/ee/user/project/issue_board.html#multiple-issue-boards).
 
+### Import Issues from CSV
+
+From the project-level issues list, you can find the import button near the "Edit issues" button in the upper-right
+side.
+
+![Import CSV button](img/import_csv_button.png)
+
+Learn more about [importing issues from CSV](csv_import.md)
+
 ### External Issue Tracker
 
 Alternatively to GitLab's built-in Issue Tracker, you can also use an [external