dxFeed send heartbeat

[mxiao-cll]

Closes #OPDATA-5381

Send heartbeat once every 10s (default value) to keep connection open

Quality Assurance

• If a new adapter was made, or an existing one was modified so that its environment variables have changed, update the relevant infra-k8s configuration file.
• If a new adapter was made, or an existing one was modified so that its environment variables have changed, update the relevant adapter-secrets configuration file.
• If a new adapter was made, or a new endpoint was added, update the test-payload.json file with relevant requests.
• The branch naming follows git flow (feature/x, chore/x, release/x, hotfix/x, fix/x) or is created from Jira.
• This is related to a maximum of one Jira story or GitHub issue.
• Types are safe (avoid TypeScript/TSLint features like any and disable, instead use more specific types).
• All code changes have 100% unit and integration test coverage. If testing is not applicable or too difficult to justify doing, the reasoning should be documented explicitly in the PR.

[changeset-bot]

🦋 Changeset detected

Latest commit: 932d241

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@chainlink/dxfeed-adapter	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR