Core Rule Set: gitea's ordinary requests pass by default (closes #198)

The eighth change, internal/waf/gitea.conf, has some fields skip the
rules that refused ordinary gitea requests there, on gitea's paths only:
searches, file names and branch names. Referer skips 944130 too. A
registry's layer reuse skips 932260 on from, the seventh change.

The new setting SWWAF_CORE_RULE_SET_EXCLUSIONS_FILE loads an operator's
own exclusions before the Core Rule Set's rules. The start stops, in
every mode, on a set file that cannot be read or does not parse, names
smallwebwaf's own ids, or holds a directive such as SecRuleRemoveById.

A test sends the recorded gitea requests at the defaults, none refused,
and three attacks, all refused.

Model: opus-5-5

docs/settings.md

@@ -191,6 +191,15 @@ chooses between the two (see "The image's command" below).
   the Core Rule Set reads, a size of at most `64K`. A question carries no more
   of a body than 64 KiB, and the Core Rule Set reads at most 64 KiB less one
   byte of it, whatever the value (see "The answer" in [`SPEC.md`](../SPEC.md)).
+- `SWWAF_CORE_RULE_SET_EXCLUSIONS_FILE` (default unset): a file of Core Rule Set
+  exclusions, written as Coraza directives. It is loaded before the Core Rule
+  Set's rules, so it holds only `SecAction` and `SecRule` lines that exclude
+  with `ctl:ruleRemoveTargetById` or `ctl:ruleRemoveById`. A file that cannot be
+  read or does not parse stops the start, whatever `SWWAF_WAF_MODE` is. So does
+  a file that names a number from 900000 to 900999 outside a comment, alone or
+  in a range. So does a directive that removes or changes rules as the file
+  loads, such as `SecRuleRemoveById`, since none of the Core Rule Set's rules is
+  loaded yet. It has no `_FILE` form.
 - `SWWAF_ERROR_BURST_THRESHOLD` (default `30`): the most refusals of one client
   in a minute (see "Attack detection" in `SPEC.md`). A count or `off`.