feat: add support for skills

[twishabansal]

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[helloeve]

Thank you Twisha for authoring this PR! After looking at the generated config, I realized there should be some improvements done to the skill generation logic we previously introduced.

• As Averi pointed out, the env variable placeholder for defining the sources are not propagated as the current generation logic will rely on the parsed version of the environment variable rather than leaving it as a placeholder.
• The generated skill.md is too large and I think we may want to move the tool-specific parameter definition into its own file under references/ to take advantages from skill's dynamic loading capability.