add constants command for latex

Author: mzuenni

spec/2023-07-draft.md

@@ -392,13 +392,13 @@ where `name` is one of the names defined in `constants`.
 Tags {% raw %}`{{xyz}}`{% endraw %} containing a name that is not defined are not modified but may be warned for.
 
 All constant sequences in the following files will be replaced by the value of the corresponding constant:
-- problem statements
 - input and output validators
 - included code
 - example submissions
 - `testdata.yaml`
 
 Constant sequences are **not** replaced in test data files or in `problem.yaml` itself.
+Note that constants are also available in the problem statements via the dedicated command `\constant{name}`.
 
 ## Problem Statements
 
@@ -448,6 +448,7 @@ It shall also provide the following commands:
   It is an error to use `\nextsample` when there are no remaining sample test cases.
 - `\remainingsamples`, tells the judge system to include all sample test cases that have not previously been included by `\nextsample`.
   It is allowed to use `\remainingsamples` even if there are no remaining sample test cases, which will simply include nothing.
+- `\constant{name}` evaluates to the value of the corresponding constant, see [constants](#constants).
 
 Arbitrary LaTeX is not guaranteed to render correctly by HTML-based judging systems.
 However, judging systems must make a best effort to correctly render **at minimum** the following LaTeX subset when displaying a LaTeX problem statement: