Exposure functions, Survival and Resistance

[virgile-baudrot]

Description

[Describe what this PR adds to the package]

Changes (choose one only, with x or click after creating PR):

• [x] New formulation/rule
• [ ] Documentation
• [ ] Bug fix for existing rules (non-breaking syntax)
• [ ] Major change to existing rules (breaking syntax, needs a breaking version bump)

Checklist:

• [ ] My code follows the BlueStyle style guide
• [x] My code is commented with explanations of anything hard to understand
• [x] There are no unnecessary or unrelated code changes included in this PR
• [x] There are no depencecies added: if so, please consider if they are necessary and explain why they are required

For bugfixes

• [ ] My PR addresses a single bug/connected group of bugs
• [ ] I have included a test that will ensure the bug does not recur

For new Rules

• [ ] My PR is limited to a clear theme/cenceptual unit. (Otherwise make multiple PRs that can be discussed separately)
• [x] New rules have tests in a file of the same name as the rule file, e.g. /test/newrulename.jl
• [ ] I have cited the source of the new formulation/s, if applicable
• [ ] I have added a documentation string to formulation struct/s, and added an entry in the docs

[virgile-baudrot]

It's just a Draft pull request, I've to check all the PR points are ok to be ready for review

[virgile-baudrot]

well, I'm going to revise my PR...

[virgile-baudrot]

Fine, I close this one and reopen new oneS with your suggestions 👍