add `atLeastLazy` method (#40)

[CogentRedTester]

Add the atleastLazy method

• [ ] This PR only introduces changes to documentation.
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• [x] This PR adds new functionality
  • [x] Is there a related issue?
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  • [x] Does the code style reasonably match the existing code?
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  • [x] Are the changes documented in the readme with a suitable example?
  • [x] Is the table of contents updated?
  • [x] Is the index.d.ts file updated, using appropriate types and using the same description as the readme?
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This adds a new function to implement lazy atLeast behaviour. This should be the last lazy quantifier (except for exact where a greedy modifier doesn't seem to make sense).

This should resolve #40.

[CogentRedTester]

Sorry, I said I wasn't going to do any more PRs, but I noticed a couple of extra gaps in the existing methods.

[francisrstokes]

Apologies that this took more than a year to merge. I've been a bit backlogged with other things