docs: miscellaneous small docs fixes

From gst-docs!166 (closed):

docs: plugin-dev: basics-boilerplate: fix typo in variable name

From gst-docs!164 (closed):

docs: tutorials: playback-3: flesh out build instructions
Add information about how to compile this file. The code in this
tutorial also requires `gstreamer-audio-1.0`, so we cannot use
the commands from the previous tutorial.

From gst-docs!159 (closed):

docs: tutorials: add link to Rust version of the tutorials

gst-docs!158 (closed):

docs: installing-on-windows: mention packages to download

From gst-docs!157 (closed):

plugin-development: basics: boilerplatr: Remove unneeded meson.build edit step

From gst-docs!106 (closed):

docs: installing-on-macos: flesh out instructions what to download

From gst-docs!34 (closed):

docs: app-dev: events: seeking: use CLOCK_TIME_NONE instead of -1 and fix parameter names
to match the parameter names in the gst_element_seek() declaration.