Simplify the version bump process. ### Description

Simplify the version bump process.

- Use substitution hook in docs to update CDN URL.
  - In `dev` or `prerelease` versions, it will point to `dev` url
  - In `stable` versions, it will point it `vX.Y.Z` url
- Introduce a version bump script `tools/bump_version.py`.


~- Use `bump2version` to bump Python versions (continuing from #2460)~
~- Use `npm version` to bump JS versions~
~- Update `run_docker` script to use latest deployed pre-built docker image when `--pre-built` option is specified.~

### Checklists

- [x] Add new / update outdated documentation

# from: http://stackoverflow.com/questions/17112550/python-and-numba-for-vectorized-functions
# setup: import numpy as np ; N = 100000 ; a, b, c = np.random.rand(N), np.random.rand(N), np.random.rand(N)
# run: vibr_energy(a, b, c)

# pythran export vibr_energy(float64[], float64[], float64[])
import numpy


def vibr_energy(harmonic, anharmonic, i):
    return numpy.exp(-harmonic * i - anharmonic * (i**2))

# from: http://stackoverflow.com/questions/17112550/python-and-numba-for-vectorized-functions
# setup: import numpy as np ; N = 100000 ; a, b, c = np.random.rand(N), np.random.rand(N), np.random.rand(N)
# run: vibr_energy(a, b, c)

# pythran export vibr_energy(float64[], float64[], float64[])
import numpy


def vibr_energy(harmonic, anharmonic, i):
    return numpy.exp(-harmonic * i - anharmonic * (i**2))
