docs: update broken hyperlinks to docs (#591)

Author: neiforfaen

README.md

@@ -8,10 +8,10 @@ Comprehensive documentation is available at [docs.slack.dev/tools/slack-github-a
 
 Use this GitHub Action to:
 
-- [Send data with a webhook to start a workflow in Workflow Builder](https://docs.slack.dev/tools/slack-github-action/sending-techniques/sending-data-webhook-slack-workflow).
-- [Send data using a Slack API method and a secret token with required scopes](https://docs.slack.dev/tools/slack-github-action/sending-techniques/sending-data-slack-api-method/).
-- [Send data as a message with a Slack incoming webhook URL](https://docs.slack.dev/tools/slack-github-action/sending-techniques/sending-data-slack-incoming-webhook/).
-- [Run Slack CLI commands with a service token](https://docs.slack.dev/tools/slack-github-action/sending-techniques/running-slack-cli-commands/).
+- [Send data with a webhook to start a workflow in Workflow Builder](https://docs.slack.dev/tools/slack-github-action/sending-data-webhook-slack-workflow)
+- [Send data using a Slack API method and a secret token with required scopes](https://docs.slack.dev/tools/slack-github-action/sending-data-slack-api-method/)
+- [Send data as a message with a Slack incoming webhook URL](https://docs.slack.dev/tools/slack-github-action/sending-data-slack-incoming-webhook/)
+- [Run Slack CLI commands with a service token](https://docs.slack.dev/tools/slack-github-action/running-slack-cli-commands/)
 
 ## Project details