Add support for adding ResX `comment`s via XMLDoc `remark`s

[ItsShamed]

For example, an input of:

/// <summary>
/// "hello"
/// </summary>
/// <remarks>
/// This is addtional useful context for translators
/// </remarks>
public static LocalisableString MyString => new TranslatableString(getKey(@"my_string"), @"hello");

would output the following to the ResX file:

<data name="my_string" xml:space="preserve">
  <value>hello</value>
  <comment>This is additional useful context for translators</comment>
</data>

This will then display the comment as a context in Crowdin¹.

---

The rationale is that some translations of strings are dependent on the context in some languages, and it's hard for translators that do not often follow client development outside of releases to accurately translate without that context.

I have a branch with a sketch implementation at master...ItsShamed:65-add-support-for-adding-comments-via-remarks

Footnotes

1. https://store.crowdin.com/resx ↩

[peppy]

This would require actually having remarks, which we don't right now. I think it's better to just clarify on the crowdin end when required, since it's probably quite seldom required?