Update handbook page for Pairify

[Pairify](https://gitlab.com/gitlab-com/support/toolbox/pairify) is a Slack bot application that will scan monitored Slack channels on a schedule for any conversations reacted with ![Pairify emoji](/images/support/workflows/assets/pairify.png "Pairify emoji") (`:pairify:`).

It will then extract all Zendesk URLs, GitLab URLs (epics, issues, merge requests, handbook and docs), Slack participants/mentions and automatically create a pairing issue with the extracted URLs, participants (converted to GitLab.com usernames) and closes out the issue.

It will then extract all Zendesk URLs, GitLab URLs (epics, issues, merge requests, handbook and docs), Slack participants/mentions and automatically create a pairing issue with the extracted URLs, participants (converted to GitLab.com usernames) and closes out the issue. The raw Slack thread is also captured in the issue, however attachments remain in Slack.

![Pairify demo](/images/support/workflows/assets/pairify_demo.gif)

Pairify will then:

1. Extract any Zendesk URLs, participants and mentions within the conversation

1. Extract the raw Slack conversation (excluding attachments)

1. Convert all Slack users to their GitLab.com counterparts

1. Create a GitLab issue in the [Support Pairing](https://gitlab.com/gitlab-com/support/support-pairing) project with the details extracted. The `pairify` label will be automatically applied to the issue, along with any other labels determined during processing.

1. Creates a message on the conversation thread indicating that the conversation has been processed. The response will also include a link to the issue created

Pairify can apply additional labels to pairing issues to indicate the pairing session type if you react with additional emojis.

The reactions in this table are mutually exclusive - Pairify will only process the first reaction added to the conversation if multiple reactions are found:

The reactions are mutually exclusive - Pairify will only process the first reaction added to the conversation if multiple reactions are found.

| Emoji                                                                                                     | Shortcode        | Description                                            |

|-----------------------------------------------------------------------------------------------------------|-------------------|-------------------------------------------------------|

| ![Crush emoji](/images/support/workflows/assets/pairify_crush.png "Crush emoji")                          | `:crush:`         | Adds the `crush` label to the pairing issue           |

| ![Customer call emoji](/images/support/workflows/assets/pairify_customer-call.png "Customer call emoji")  | `:customer_call:` | Adds the `customer-call` label to the pairing issue   |

| ![Office hours emoji](/images/support/workflows/assets/pairify_office-hours.png "Office hours emoji")     | `:office-hours:`  | Adds the `office hours` label to the pairing issue    |

See [specifying the pairing issue type](https://gitlab.com/gitlab-com/support/toolbox/pairify#specifying-the-pairing-session-type) for more information.

To ensure these reactions are picked up by Pairify, you should add these reactions before adding the `:pairify:` emoji to your conversation.

## Automatic labels

Pairify automatically applies certain labels based on the content and context of pairing sessions. For a complete list of automatic labels, see [automatic labels](https://gitlab.com/gitlab-com/support/toolbox/pairify#automatic-labels) for more information.

## Reminders

Pairify can also send automatic reminder messages for idle threads. See [reminders](https://gitlab.com/gitlab-com/support/toolbox/pairify#reminders) for more information.

## Channels monitored by Pairify