docs(metrics): extract Metrics code snippets in separate files

[niko-achilles]

Description of your changes

The code snippets are extracted to their own separate files, placed under docs/snippets/metrics.
And project documentation in docs/core/metrics.md references the code snippets, which are extracted to their own separate files.

Code snippets of metrics created, in path docs/snippets/metrics:

1. basicUsage.ts
2. sam.ts
3. createMetrics.ts
4. customDimensions.ts
5. multiValueMetrics.ts
6. defaultDimensions.ts
7. defaultDimensionsMiddy.ts
8. setDefaultDimensions.ts
9. defaultDimensionsDecorator.ts
10. middy.ts
11. decorator.ts
12. manual.ts
13. throwOnEmptyMetrics.ts
14. captureColdStartMetricMiddy.ts
15. captureColdStartMetricDecorator.ts
16. addMetadata.ts
17. singleMetricDifferentDimsMiddy.ts
18. singleMetricDifferentDimsDecorator.ts

Each code snippet is referenced as --8<-- "docs/snippets/metrics/.ts" in docs/core/metrics.md .

TODO items:

1. Lint code snippets created in path docs/snippets/metrics by using current eslint rules that are used for packages managed by monorepo as workspaces
2. Correct code snippets by consulting the eslint findings.
3. May Adjust the eslint configuration to documentation needs, e.g. allow any type or adjust the code snippets by removing event and context from the handler signature .
4. introduce docs/snippets/metrics as workspace in package.json managed by monorepo . This will enable to reuse the .tsconfig.es.json used by workspaces in monorepo or to identify the need to improve .tsconfig.es.json, e.g. introducing noEmit: true which signals to a dev. that the tsconfig.es.json file is used for linting/dev. purposes only. Also the tsconfig file used for linting should have the experimentalDecorators: true .

How to verify this change

Modified docs/core/metrics.md
Added code snippets as .ts files in path docs/snippets/metrics

Related issues, RFCs

Issue number: #1221 #729

PR status

Is this ready for review?: YES
Is it a breaking change?: NO

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding changes to the examples
• My changes generate no new warnings
• The code coverage hasn't decreased
• I have added tests that prove my change is effective and works
• New and existing unit tests pass locally and in Github Actions
• Any dependent changes have been merged and published
• The PR title follows the conventional commit semantics

Breaking change checklist

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[niko-achilles]

@dreamorosi please review this commit and read the TODO items described in the comment.
Have documented the TODOS for continuation to our work in context of code snippets and docs.

this PR solves issue #1221

[dreamorosi]

Could you please change the line above (L128) to:

    ```typescript hl_lines="7 9"

this is not an error you introduced but I just noticed that the highlighted lines are not correct, so let's fix it.

[niko-achilles]

@dreamorosi , sure, take a look .

[dreamorosi]

@niko-achilles could you please rebase the branch before we merge it? I see the diff from other commits are here.

git checkout main
git fetch origin
git pull origin main
git checkout my_branch_name
git rebase main
... 
git push origin my_branch_name -f

[dreamorosi]

Thanks for addressing the comments, could you please rebase the branch (see previous message).

[niko-achilles]

@dreamorosi now we have 2 commits as expected , thanks for the command tips