## Allow regular expressions after ": "
BUG: 361875
Previously, after `text: `, `[]: ` or `$text=: ` regular expressions weren't highlighted (the `check_div_1` context prevents highlighting regex, similar to `NoRegExp` context in "javascript.xml"). Regular expressions are allowed there, so they will now be highlighted.
{F6539652}
## Don't highlight HEREDOC in singleton class definition (operator <<)
BUG: 358273
Now, after the keyword "class", Heredoc's will not be highlighted [1]. For example:
{F6539653}
Before, `<<Foo` was highlighted as Heredoc.
I did some tests in Ruby 2.6.0, 2.5.1 and 2.3.8, and Heredoc isn't considered in the code: `class <<Foo`, `class <<21`, `class <<"Foo"` or `class <<-Foo`, so I can say that the fix is correct.
## Improvements in HEREDOC:
* Add squiggly HEREDOC (introduced in Ruby 2.3) [2][3]
For example: `<<~HEREDOC`
* Backticks can surround identifiers [3]. Example: <<-`HEREDOC`
* Improve highlighting of identifier quotes. Now you need to close quotes to highlight the HEREDOC.
For example, HEREDOC was previously highlighted as: `<<"HEREDOC` , `<<HEREDOC"`
I also added a modeline to force the use of tabs as an indentation, since the file uses tabs.
**References:**
* [1] Ruby/Rails Programming. Singleton Classes in Ruby (aka eigenclasses): https://codequizzes.wordpress.com/2014/04/11/singleton-classes-in-ruby-aka-eigenclasses/
* [2] Infinum. Multiline strings in Ruby 2.3 - the squiggly heredoc: https://infinum.co/the-capsized-eight/multiline-strings-ruby-2-3-0-the-squiggly-heredoc
* [3] Ruby-doc.org. Here Documents: https://ruby-doc.org/core-2.5.1/doc/syntax/literals_rdoc.html#label-Here+Documents