Add i18n consideration checkbox

[himorin]

Added as checkbox.

• It seems there is no option to add checkbox as a child of other input field, e.g. attached sub-item to specification URL input box. So added at right below the input field of specification URL.
• fixed several markdown syntax error at request-review-for-a-fpwd.yml (should be a separated PR??)
• description is linked to a hash URL used for current editors' draft at github.io. so, hash will not be active until next publication to /TR/ of specdev.
• check form sample at e.g. https://github.com/himorin/i18n-request/blob/add-i18n-consideration/.github/ISSUE_TEMPLATE/request-CR-review.yml

[himorin]

Thank all for review. merging.