Cache HTML rewriting function signature

[benoit74]

This PR replaces #371 with another approach based on @lru_cache

Fix #370

Changes:

• use @cache (an @lru_cache without max size since we want to cache all values) to cache rewriting rule function signature

[benoit74]

Compared to the approach propose in #371, performance seems almost identical, this approach is only marginally slower (19.8 secs vs 19 secs)

[rgaudin]

OK ; Better rely on stdlib if we can 👍