Allow installing static lib

[m-kuhn]

This builds and installs either the static or shared lib.
The behavior is controlled through BUILD_SHARED_LIBS.

cmake -DBUILD_SHARED_LIBS=OFF will build as static library.

The default is a dynamic library to replicate the original behavior of installing a shared library if no options are provided.

Aligns the target namespace with the package name (lowercase lazperf).
Internally uses the namespaced target lazperf::lazperf for linking.

Implements #168

[dg0yt]

Only a cursory review, coming from the vcpkg PR.

[dg0yt]

If you want the lib target to stand out where used here and downstream, do the next step and add a namespaced alias.

Suggested change

	lazperf_add_library(${LAZPERF_LIB} ${SRCS})
	lazperf_add_library(lazperf ${SRCS})
	add_library(lazperf::lazperf ALIAS lazperf)

(IDK if it should be here or in lazperf_add_library.)

[m-kuhn]

There's a namespace defined in install.cmake, would that need to be dropped instead?

laz-perf/cmake/install.cmake

Lines 27 to 28 in 2c21fa0

	NAMESPACE
	LAZPERF::

[dg0yt]

If the namespace is already defined, it should be used.
Nothing needs to be dropped from installation. The proposed alias is for sub-project usage.
So it wouldn't matter downstream if the project is used as a sub-project or from an installation.

(LAZPERF::lazperf? TBH I prefer when package name, namespace and main target do not use different spellings. There could be LAZPERF::LAZPERF or lazperf::lazperf.)

[m-kuhn]

Proposed lazperf::lazperf now since package and target already are lowercase, so namespace is now aligned too. I am open to reverting that if this is not desired.

[m-kuhn]

Thanks @dg0yt

[hobu]

Windows and wasm builds not healthy with these changes.

[hobu]

wasm build still failing with

CMake Error at cmake/functions.cmake:4 (lazperf_install_library):
Unknown CMake command "lazperf_install_library".