Add `schedule_every` setting

[BBQigniter]

Please, add schedule_every setting to allow schedules with less then a minute interval as the cronline only allows. It seems the rufus-scheduler can interpret for example 10s which would be great.

BTW, I tried to have a look at building this plugin but bundler install cannot resolve the dependencies:

ruby --version
jruby 9.3.3.0 (2.6.8) 2022-01-19 b26de1f5c5 OpenJDK 64-Bit Server VM 17.0.2+8-Ubuntu-120.04 on 17.0.2+8-Ubuntu-120.04 +jit [linux-x86_64]

bundle install
Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies.................................................................................................................................................................................................................................................
Bundler could not find compatible versions for gem "elasticsearch":
  In Gemfile:
    logstash-input-elasticsearch was resolved to 4.12.2, which depends on
logstash-core-plugin-api (>= 1.60, <= 2.99) was resolved to 2.1.26, which
depends on
        logstash-core (= 5.5.0) was resolved to 5.5.0, which depends on
          elasticsearch (>= 5.0.4, ~> 5.0)

    logstash-input-elasticsearch was resolved to 4.12.2, which depends on
      elasticsearch (>= 7.14.0)

Bundler could not find compatible versions for gem "logstash-core":
  In Gemfile:
    logstash-input-elasticsearch was resolved to 4.12.2, which depends on
logstash-core-plugin-api (>= 1.60, <= 2.99) was resolved to 1.60.1, which
depends on
        logstash-core (<= 2.4.99, >= 2.4.0.snapshot1)

    logstash-input-elasticsearch was resolved to 4.12.2, which depends on
logstash-mixin-ecs_compatibility_support (~> 1.3) was resolved to 1.3.0,
which depends on
        logstash-core (>= 6.0.0)

[andsel]

@BBQigniter I would suggest to use a local clone of the Logstash repository and then set

export LOGSTASH_PATH=<path_to_logstash_source> && export LOGSTASH_SOURCE=1

then use

bundle install

and test with

bundle exec rspec