Translate UI text for new strings

[mmistakes]

As part of #424 several new text strings need translating in /_data/ui-text.yml. Pull requests welcome 😄

• Spanish
• Brazilian Portuguese
• Turkish
• Italian
• French

comments_title             : "Comments"
comment_form_info          : "Your email address will not be published. Required fields are marked"
comment_form_comment_label : "Comment"
comment_form_md_info       : "Markdown is supported."
comment_form_name_label    : "Name"
comment_form_email_label   : "Email address"
comment_form_website_label : "Website (optional)"
comment_btn_submit         : "Submit Comment"
comment_btn_submitted      : "Submitted"
comment_success_msg        : "Thanks for your comment! It will show on the site once it has been approved."
comment_error_msg          : "Sorry, there was an error with your submission. Please make sure all required fields have been completed and try again."
loading_label              : "Loading..."

[rschaerer]

In my opinion you would have a more relaxed ☺️ time concerning the "by no means a full-on i18n solution" feature, if you would add all the missing strings in English to the several different translations and append a comment like # translation missing to the corresponding lines like so:

# Turkish
# -----------------
tr: &DEFAULT_TR
  page                       : "Sayfa"
  [...]
  undefined_wpm              : "_config.yml dosyasında tanımlanmamış words_per_minute parametresi"
  comment_form_info          : "Your email address will not be published. Required fields are marked" # translation missing
  [...]

Otherwise the empty keys in the translations which lead to omitting them from view might confuse users which switch the language and didn't read the docs carefully.

How do you think about this? If you agree, I could do the work and create a PR for this.

[mmistakes]

My thought was empty keys fallback to English (what the theme currently does), which should hopefully be a clue when switching languages that they're missing.

Example: {{ site.data.ui-text[site.locale].comments_label | default: "Comments" }}

Previously they were just blank and I noticed quite a few forks where half of the UI text was missing. So I added the English default values as a nudge to consult the docs for those who actually care about such things.

Open to suggestions on ways of better surfacing these sorts of things without making it a maintenance headache or junking up things too much.

[rschaerer]

😄 Ok, I couldn't read the docs and just tried to remove follow_label, which is intended to be omittable. I think the actual fallback to default is exactly what I was thinking about. Thank you for elaborating this to me!

[mmistakes]

#1278