update toc of pipelineruns.md

[pritidesai]

https://github.com/tektoncd/pipeline/blob/main/docs/pipelineruns.md has an outdated ToC.

Please update it to include:

• Move Specifying Resources to the same level as Specifying Parameters.
• Add missing titles (1) Implicit Parameters (2) Gracefully*

Add and tags for inplace ToC updates in the future such as:

mdtoc --inplace docs/pipelineruns.md

/kind documentation
/good-first-issue

[tekton-robot]

@pritidesai:
This request has been marked as suitable for new contributors.

Please ensure the request meets the requirements listed here.

If this request no longer meets these requirements, the label can be removed
by commenting with the /remove-good-first-issue command.

In response to this:

https://github.com/tektoncd/pipeline/blob/main/docs/pipelineruns.md has an outdated ToC.

Please update it to include:

• Move Specifying Resources to the same level as Specifying Parameters.
• Add missing titles (1) Implicit Parameters (2) Gracefully*

Add and tags for inplace ToC updates in the future such as:

mdtoc --inplace docs/pipelineruns.md

/kind documentation
/good-first-issue

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[koneko096]

may i take this?

[pritidesai]

may i take this?

yes please, thank you @koneko096. 🙏 Please let me know if you need any help with this.