* Update docker.rb

* format: change double quotes to single quote

The Velocity lexer includes a rule that incorrectly spells the `:push`
magic state as `:push!`. This causes an error when lexing brackets
(which match this rule). This commit fixes that mistake.

* used 'Enumerator#with_index' to detect lineno.

* Changing variable names

* 'tokens_in_line' -> 'line_tokens'
The names of variables used as "line_tokens" in html_line_table and html_linewise files should be changed to match the names of those files.

The `continue` keyword is missing from the list of keywords. This
commit adds it.

The C++ lexer uses `_` as a digit separator for binary literals. This
is syntactically incorrect. The digit separator in C++ is `'`. This
commit fixes that error.

Co-authored-by: Stuart <stuart.wheaton@jhuapl.edu>
Co-authored-by: Michael Camilleri <mike@inqk.net>

The PowerShell lexer includes a hash table state as a special case and
is not tested on more complex tables (e.g. including comments and
code). This commit factors out the hash table state into a more generic
`:expr` state that can handle more complex structures.

This commit also reduces the overall level of highlighting. This 
improves the visibility of the more important syntax.

Rouge will currently match identifiers in the Kotlin lexer that begin
with certain keywords (such as `super`). This is because of a change in
#1496 that added a rule to support labels. That change should have
updated the rule to end with a `\b` so as to ensure that identifiers
that begin with the listed keywords are followed by a word break.
This commit fixes that error.

The Batchfile lexer does not support 'long options' (i.e. options that
begin with --). This commit adds support for that.

Perl supports a variety of different sigils (`$`, `@`, `%`, etc). This
commit improves support for some of the more unusual combinations of
sigils.

The maintenance changes in #1548 resulted in updates to two rules in
the Ruby lexer, one regarding regular expression flags and the other
regarding heredoc strings. However, these patterns should not have been
changed. The change in #1548 was to prevent rules that matched an empty
string unless they contained a 'predicate' of some sort. Both rules in
the Ruby lexer contained such a predicate and so should not have been
changed. This commit fixes that error.

The changes made in #1548 to avoid empty regular expression patterns,
broke the template string rules in the JavaScript lexer (and lexers
such as the TypeScript lexer that inherit from it). This commit adds the
rules necessary to fix this lexing.

While #1595 improved the lexing of more complex structures, the
PowerShell lexer is limited in its support for nested data structures.
This commit moves more of the syntax for representing values from the
`:root` state to the `:expr` state so that this syntax can work when
nested.