This commit adds the compiler subpackage to implement issue #25.
The compiler subpackage currently contains abstract base classes
and will receive implementations later.

The RegexParser is a Parser implementation identifying
the start and end of a code section with regular expressions.
This is the standart implementation modified to implement issue #25.

- add CompileError for exceptions during compiling
- replace Mapping in Code.execute with Dict because exec needs a dict
- move line offset handling from CodeBuilder to Parser
- replace name and loader with ModuleSpec

This commit changes RegexParser to comply to the new abc.
Furthermore, CompileError is changed to show the section which failed.

This commit adds the current implementation of code objects to the compiler subpackage.
This requires to raise the minimal python version to 3.8 as stated in issue #25.

This is necessary because the generic code implementation requires the
CodeType.replace method, which is available in python 3.8+.

This commit adds a facade to the compiler subsystem as mentioned in issue #25.

This commits adds the dedenting feature as a decorator as mentioned in issue #25.

To allow for better testing, the code for detecting code lines is moved into a seperate method.

Before this commit, every builder kept track the section number themself,
resulting in redundancy and susceptibility to errors.
This commit modifies compiler.CodeBuilder.add_* to accept the current section number.

This commit adds a implementation of compiler.Code in python bytecode as mentioned in issue #25.
It is implemented using a generator and currently slower than the generic implementation to
allow for variables to be passed to .execute.
If MAKE_FUNCTION gets faster or the compiler subsystem gets changed it may be faster.

This commit replaces a few type hints in the compiler subpackage with generics.
This allows detaching a CodeBuilderDecorator which was detached from another CodeBuilderDecorator
and fixes the result of CodeBuilder.copy() not having the same type as his 'parent'.

To allow for better error discovery, this commit replaces CompileError with
a normal SyntaxError with the correct line number set.

To allow for Python version 3.7 to be used, GenericCodeBuilder now uses the ast module
instead of CodeType.replace.

This commit updates the workflow to not run MyPy on pypy-3.7 because it is not supported.