[Admin/Chronology block] Verify that the admin can add a new context.

**Priority:**
High

**Preconditions**

1. The "StreetCode page" is opened.

2. Logged as admin.

**Steps to reproduce**

1. Scroll down to the "Chronology" block.

2. Сlick on the '+' button.

3. Сlick on the context field:

- Enter the category title (e.g. Голодомор).
- Copy the name and paste it into the field.

4. Click Enter or near the field.

**Expected result**
The entered text is in the field and highlighted in gray.

**User story:**
#124

**Related bug:**
#401