Move copyright notices down the title in docs

Otherwise Docusaurus can't see the document's title

Make Pistache REUSE compliant

Reuse is a specification that aims at making licensing of open source
software easier. You basically have to include an SPDX header in all
files, and when this isn't possible you create a file named
filename.license containing the header. While I find this a bit too much
this is also the only way of reliably determining the license and the
copyright holder of a certain file.

The use of SPDX tags has been adopted by projects like the Linux Kernel
(torvalds/linux/commit/a61127c2130236168321cc76c5a58e15c00ad154),
systemd, etc, and I find it way better that including a long copyright
notice on top of every file.

I didn't add any email address, but if you'd like to it is completely
possible to add them in the SPDX-FileCopyrightText tag, between angle
brackets.

The specification is available on https://reuse.software

Make date.h and cpp-httplib proper dependencies

New connections can come from either IPv4 or IPv6 addresses. Hence, use
a sockaddress structure that can handle both.

Bumps [normalize-url](https://github.com/sindresorhus/normalize-url) from 4.5.0 to 4.5.1.
- [Release notes](https://github.com/sindresorhus/normalize-url/releases)
- [Commits](https://github.com/sindresorhus/normalize-url/commits)

---
updated-dependencies:
- dependency-name: normalize-url
  dependency-type: indirect
...
Signed-off-by: dependabot[bot] <support@github.com>

If someone is building Pistache from source as a subproject they are not
going to commit any changes from there, and setting up the pre-commit
hook is pointless.
It is now also optional, since git is not stictly needed to build the
library, and if you don't have git installed you are probably not going
to commit.

Otherwise Debian packaging wouldn't be possible.

listener: use sockaddr_storage for socket addrs

Update Docusaurus to beta 0

Bump normalize-url from 4.5.0 to 4.5.1 in /pistache.io

Bumps [normalize-url](https://github.com/sindresorhus/normalize-url) from 4.5.0 to 4.5.1.
- [Release notes](https://github.com/sindresorhus/normalize-url/releases)
- [Commits](https://github.com/sindresorhus/normalize-url/commits)

---
updated-dependencies:
- dependency-name: normalize-url
  dependency-type: indirect
...
Signed-off-by: dependabot[bot] <support@github.com>

New connections can come from either IPv4 or IPv6 addresses. Hence, use
a sockaddress structure that can handle both.

They were previously embedded in the source tree, and are now proper
subprojects.
I've also moved rapidjson.h out of include/pistache/thirdparty since it
is part of Pistache - this is a breaking change.

Set up commit hook only if master project and make it "optional"

If someone is building Pistache from source as a subproject they are not
going to commit any changes from there, and setting up the pre-commit
hook is pointless.
It is now also optional, since git is not stictly needed to build the
library, and if you don't have git installed you are probably not going
to commit.

Add pre-commit format hook

Complete #933

As always, I fogot about something

Fix some compiler and clang-tidy warnings

Use `override`, `= default` instead of `{}`, remove std::moves of const&
objects, use `[[maybe_unused]]`, use `nullptr` instead of `0`, rename
function parameters so that they are the same in declarations and
definitions, use `const auto&` instead of `const auto` when appropriate,
use structured bindings, use C++ casts instead of C-style casts, use
`.empty()` instead of `.size() == 0`, use `.emplace_back()` when
appropriate, use bool literals instead of `0` and `1`,  use `auto*`
instead of `auto`, fix #928, close #897

Use std::string_view

Bump ws from 6.2.1 to 6.2.2 in /pistache.io

include/view.h is now unused, and could be removed, even though I would
keep it untill C++20 (std::span)

Bumps [ws](https://github.com/websockets/ws) from 6.2.1 to 6.2.2.
- [Release notes](https://github.com/websockets/ws/releases)
- [Commits](https://github.com/websockets/ws/commits)

---
updated-dependencies:
- dependency-name: ws
  dependency-type: indirect
...
Signed-off-by: dependabot[bot] <support@github.com>

Nested namespaces

Bump dns-packet from 1.3.1 to 1.3.4 in /pistache.io

Bumps [dns-packet](https://github.com/mafintosh/dns-packet) from 1.3.1 to 1.3.4.
- [Release notes](https://github.com/mafintosh/dns-packet/releases)
- [Changelog](https://github.com/mafintosh/dns-packet/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mafintosh/dns-packet/compare/v1.3.1...v1.3.4)
Signed-off-by: dependabot[bot] <support@github.com>