docs: update bug-report template and README

[tatomyr]

What/Why/How?

Clarified the bug report template.
Updated README to be more general in terms of capabilities: OpenAPI -> API.

Security

• The security impact of the change has been considered
• Code follows company security practices and guidelines

[changeset-bot]

⚠️ No Changeset found

Latest commit: 9a551dd

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[github-actions]

Command	Mean [s]	Min [s]	Max [s]	Relative
redocly lint packages/core/src/benchmark/benches/rebilly.yaml	1.452 ± 0.031	1.407	1.500	1.00
redocly-next lint packages/core/src/benchmark/benches/rebilly.yaml	1.496 ± 0.032	1.456	1.562	1.03 ± 0.03

[tatomyr]

People often leave it as it is. I hope this change will clarify that they should write their own steps.