Several file extension, file name, and folder name icon associations

[maallaard]

Other than some general cleanup, I added some more names for folder and file icons to associate with. This includes a fair amount of abbreviations and pluralizations. The changes are as follows:

File extensions:

• json5 for json icon
• ods for table icon
• bz2 for zip icon
• odt for word icon
• odp for presentation icon
• ron for rust icon (rust object notation)

File names:

• .gitignore-global for git icon (with hyphen instead of underscore)
• contributing.md, contributing.rst, contributing.txt, and contributing for contributing icon
• readme.rst for readme icon
• changelog.rst, changes.rst, and changes for changelog icon
• credits.rst for credits icon
• authors.rst, contributors.md, contributors.rst, contributors.txt, and contributors for authors icon

Folder names:

• srcs for folder-src icon
• imgs, icos, screengrab, screengrabs, pic, and pics for folder-images icon
• jsons for folder-json icon
• cfg, cfgs, conf, and confs for folder-config icon
• langs for folder-i18n icon
• aud and auds for folder-audio icon
• vid and vids for folder-video icon
• arc, arcs, bkp, bkps, bak, and baks for folder-archive icon
• func, funcs, maths, and calcs for folder-functions icon
• pkgs for folder-packages icon
• anim and anims for folder-animations icon

I also noticed that musics is a valid name under the folder-audio icon, but since the word 'music' does not have a plural form, 'musics' is not an actual word and should be reverted.

[PKief]

Thank you very much for this nice PR! There's only one small issue with the duplicated "changes" file name, see comment.

[maallaard]

tests passed, hallelujah

[PKief]

tests passed, hallelujah

Thank you :)