<commit_before><commit_msg>Add README for informal specs directory.<commit_after>This directory contains "informal specifications".

In order to move faster and get better feedback, we implement and iterate on
language changes before the full official specification has been written. Still,
the implementers need *something* to go on.

For that, the language team writes "informal specifications". These are
intended to be precise enough for a good faith implementer to correctly
understand the syntax and semantics of the language, but without all of the
laborious detail of the complete specification.

Once the feature has been implemented, tested, and we are confident in it, the
language team will write the real text in the language specification and the
document here becomes deprecated and no longer canonical.

Until then, while the feature is in progress, a live pull request for the
informal spec is the source of truth for the feature.
{'fraction_non_alphanumeric': 0.030623020063357972, 'fraction_numerical': 0.0, 'mean_word_length': 5.1558441558441555, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 3, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '499812', 'n_tokens_mistral': 218, 'n_tokens_neox': 202, 'n_words': 142}