Fix documentation link in README files

[becky-gilbert]

Fixes #63

This PR changes the link used in the README.md file for the "See documentation" text. It includes the following changes:

• Changes the README's embedded documentation link so that it points to the documentation file created in /<package-root>/docs/<package-name>.md, rather than to the README file itself.
• Fixes broken documentation links that can be generated in some cases (e.g. contains tree rather than blob in full file URL; contains misplaced leading slash).
• Updates the interactive console prompt to say "Enter the path to the documentation file" rather than "Enter the path to the README file" (this link is used only for the documentation, and the README file location cannot be changed).
• Changes the --readme-path flag to --documentation-path, for clarity

Examples

Installing in a known repo (jsPsych contrib)

Old: points to README itself

See [documentation](https://github.com/jspsych/jspsych-contrib/packages/extension-test/README.md)

New: points to the .md file in /docs

See [documentation](https://github.com/jspsych/jspsych-contrib/blob/main/packages/extension-test/docs/extension-test.md)

Installing in an untracked (non-Git) directory or from the root of an unknown repo

Old: points back to README, and this is a broken link due to the leading slash, which makes it an absolute path from the domain root (https://github.com)

See [documentation](/extension-test/README.md)

New: relative path to docs file

See [documentation](docs/extension-test.md)

Installing in a subdirectory of an unknown repo

Old: points back to README and link is broken due to /tree/

See [documentation](https://github.com/becky-gilbert/jspsych-extension-pause/tree/main/subdirectory/extension-test/README.md)

New: points to docs file and works with /blob/ instead of /tree/

See [documentation](https://github.com/becky-gilbert/jspsych-extension-pause/blob/main/subdirectory/extension-test/docs/extension-test.md) 

Screenshots

New interactive console prompt for documentation file path, and the new default value (this was called inside an untracked directory).

p.s. Tests would be helpful... I would add tests that cover all of these cases if someone wants to add a test setup (👀 #4)

[changeset-bot]

🦋 Changeset detected

Latest commit: 41582a1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@jspsych/new-multiplayer-adapter	Minor
@jspsych/new-extension	Minor
@jspsych/new-timeline	Minor
@jspsych/new-plugin	Minor

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