[Ruby] Highlight #{} interpolation in heredoc

[zufuliu]

Per https://docs.ruby-lang.org/en/master/syntax/literals_rdoc.html#label-Here+Document+Literals
interpolation is allowed in double (or none) quoted or backtick quoted heredoc (SCE_RB_HERE_QQ and SCE_RB_HERE_QX).

# SCE_RB_HERE_Q
puts <<-'EXPECTED'
One plus one is #{1 + 1}
EXPECTED

# SCE_RB_HERE_QQ
puts <<-EXPECTED.chomp
One plus one is #{1 + 1}
EXPECTED

# SCE_RB_HERE_QX
puts <<-`HEREDOC`
cat #{__FILE__}
HEREDOC

[zufuliu]

ruby-0215.zip

Patch contains three changes:

1. Set SCE_RB_HERE_QQ and SCE_RB_HERE_QX based on HereDoc.Quoted.
2. Add InnerExpression class to encapsulate enterInnerExpression() and exitInnerExpression().
3. Highlight #{} in SCE_RB_HERE_QQ and SCE_RB_HERE_QX.

[nyamatongwe]

Included in 5.2.3.