Improve addon download refusal messages

Changes some instances of file to addon and warns the user if they cannot join due to the server adding a folder as-if it were an addon.

Contacting the server...
NOTICE: You need additional addons to connect to this server:
 * "VL_HowToDieInTwoSeconds-v1" (folder)
One or more addons was added as a folder, which the server cannot send.

added Netcode label

added 1 commit

• 57465a1a - Fix minor grammatical mistake

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resolved all threads

added 140 commits

• 57465a1a...a68440c4 - 139 commits from branch next
• 2a2fd756 - Merge branch 'next' into improve-download-refuse-message

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changed title from Improve download refusal messages to Improve addon download refusal messages

added Changed behavior Enhancement labels

added 347 commits

• 2a2fd756...106a98ce - 346 commits from branch next
• e24a9c2f - Merge branch 'next' into improve-download-refuse-message

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merged

mentioned in commit 5ef55cc6

changed milestone to %2.2.14