added workflow_dispatch

[lijamie98]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  paymentservice.stellar, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.

What

1. Document the description of the workflows if it does not seem obvious.
2. Add workflow_dispatch trigger so that we may run the workflow from GH UI.

Why

Improve the documents.

Known limitations

The Run Workflow button won't show up until it is merged to the develop branch.

[stellar-jenkins]

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