Small fixes and setup API extractor

[chgeo]

Set up API extractor → run with npm run api-extractor

Add a few fixes to allow it tun run (see below)

Fix a bunch of TSDoc comments (@example, code fences, @param)

[daogrady]

Running npm run api-extractor greets me with the following output:

➜  cds-types git:(api-extractor) ✗ npm run api-extractor

> @cap-js/cds-types@0.1.0 api-extractor
> api-extractor run --local --verbose


api-extractor 7.38.5  - https://api-extractor.com/

Using configuration from ./api-extractor.json
Analysis will use the bundled TypeScript version 5.0.4
*** The target project appears to use TypeScript 5.3.3 which is newer than the bundled compiler engine; consider upgrading API Extractor.
Writing: /Users/-/git/cds-types/temp/cds-types.api.json
Error: Unable to create the API report file. Please make sure the target folder exists:
/Users/-/git/cds-types/etc
Writing package typings: /Users/-/git/cds-types/dist/cds-types.d.ts
Warning: apis/cqn.d.ts:59:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:61:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:63:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:65:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:69:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:73:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:75:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:77:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:79:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:81:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
Warning: apis/cqn.d.ts:83:5 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration

The warnings can surely be fixed later, but we should probably look into the error.
Creating the missing folder now produces the following output:

➜  cds-types git:(api-extractor) ✗ npm run api-extractor

> @cap-js/cds-types@0.1.0 api-extractor
> api-extractor run --local --verbose


api-extractor 7.38.5  - https://api-extractor.com/

Using configuration from ./api-extractor.json
Analysis will use the bundled TypeScript version 5.0.4
*** The target project appears to use TypeScript 5.3.3 which is newer than the bundled compiler engine; consider upgrading API Extractor.
Writing: /Users/-/git/cds-types/temp/cds-types.api.json
Warning: The API report file was missing, so a new file was created. Please add this file to Git:
/Users/-/git/cds-types/etc/cds-types.api.md

Ergo:

• should we add ./etc/ to the repository? Or prefix the api-extractor script with mkdir etc && ...? The latter will probably cause issues on Windows.
• I did not find any entry in the config, so I assume "etc" is the default name. If that is not the case and we have no other point for "etc", can we find a more fitting name? "extracted-api" or similar?
• should we follow the tool's recommendation and add etc/cds-types.api.md to the repository?
• (probably beyond the scope of this PR, but as api-extractor hints at it, we might want to upgrade TS to 5.3.3)

[chgeo]

• should we add ./etc/ to the repository? Or prefix the api-extractor script with mkdir etc && ...? The latter will probably cause issues on Windows.
• I did not find any entry in the config, so I assume "etc" is the default name. If that is not the case and we have no other point for "etc", can we find a more fitting name? "extracted-api" or similar?
• should we follow the tool's recommendation and add etc/cds-types.api.md to the repository?
• (probably beyond the scope of this PR, but as api-extractor hints at it, we might want to upgrade TS to 5.3.3)

All valid points, but for a second PR.
My goal here was not to establish the extractor, but to fix some findings.

[daogrady]

Then let's postpone the proper setup of api-extractor to another PR and get these declarations merged.
Looks good to me now, thanks for brushing up the types and docs.