feat(analysis/transcendental): e is transcendental

[jjaassoonn]

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This branch contains some basic theorems about transcendental numbers. The code are not very idomatic, so helpsa re more than welcome.

[jamesa9283]

Some docstrings and a module docstrings here would be nice. If you are unsure of what I mean, look in some other files in mathlib. I believe that data/padics/padic_numbers.lean is a good example. Also it should probably be mentioned that docstrings are indicated using /-- *text* -/ for def, lemma, theorem etc and module docstrings are indicated using /-! *text* -/ and can have markdown formatting in them.

[PatrickMassot]

Some docstrings and a module docstrings here would be nice. If you are unsure of what I mean, look in some other files in mathlib. I believe that data/padics/padic_numbers.lean is a good example. Also it should probably be mentioned that docstrings are indicated using /-- *text* -/ for def, lemma, theorem etc and module docstrings are indicated using /-! *text* -/ and can have markdown formatting in them.

See also https://leanprover-community.github.io/contribute/doc.html, and https://leanprover-community.github.io/contribute/index.html in general.

[bryangingechen]

This is a pretty big PR. Can you split off any smaller PRs? For instance, I think small_lemmas.lean could potentially be a PR on its own (though those lemmas may have to go to different parts of mathlib), and the material on Liouville numbers could also be a separate PR as well.

You can leave this one open and mark it "blocked-by-other-PR" with references to the other PRs until those get merged.

[jjaassoonn]

I will split into smaller ones