CI: include automatic Pull Request Labeler

This adds GitHub CI action which makes use of 'Labeler', allowing
automatic labeling of new PRs, based on the modified files paths.

Below labels are supported and more can be added later:
- 'target/*'
- 'target/imagebuilder'
- 'kernel'
- 'core packages'
- 'build/scripts/tools'
- 'toolchain'
- 'GitHub/CI'

For more information:
https://github.com/marketplace/actions/labeler

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

.github/labeler.yml

@@ -0,0 +1,103 @@
+# target/*
+"target/airoha":
+  - "target/linux/airoha/**"
+"target/apm821xx":
+  - "target/linux/apm821xx/**"
+"target/archs38":
+  - "target/linux/archs38/**"
+"target/armvirt":
+  - "target/linux/armvirt/**"
+"target/at91":
+  - "target/linux/at91/**"
+"target/ath25":
+  - "target/linux/ath25/**"
+"target/ath79":
+  - "target/linux/ath79/**"
+"target/bcm27xx":
+  - "target/linux/bcm27xx/**"
+"target/bcm47xx":
+  - "target/linux/bcm47xx/**"
+"target/bcm4908":
+  - "target/linux/bcm4908/**"
+"target/bcm53xx":
+  - "target/linux/bcm53xx/**"
+"target/bcm63xx":
+  - "target/linux/bcm63xx/**"
+"target/bmips":
+  - "target/linux/bmips/**"
+"target/gemini":
+  - "target/linux/gemini/**"
+"target/imx":
+  - "target/linux/imx/**"
+"target/ipq40xx":
+  - "target/linux/ipq40xx/**"
+"target/ipq806x":
+  - "target/linux/ipq806x/**"
+"target/kirkwood":
+  - "target/linux/kirkwood/**"
+"target/lantiq":
+  - "target/linux/lantiq/**"
+"target/layerscape":
+  - "target/linux/layerscape/**"
+"target/malta":
+  - "target/linux/malta/**"
+"target/mediatek":
+  - "target/linux/mediatek/**"
+"target/mpc85xx":
+  - "target/linux/mpc85xx/**"
+"target/mvebu":
+  - "target/linux/mvebu/**"
+"target/mxs":
+  - "target/linux/mxs/**"
+"target/octeon":
+  - "target/linux/octeon/**"
+"target/octeontx":
+  - "target/linux/octeontx/**"
+"target/omap":
+  - "target/linux/omap/**"
+"target/oxnas":
+  - "target/linux/oxnas/**"
+"target/pistachio":
+  - "target/linux/pistachio/**"
+"target/qoriq":
+  - "target/linux/qoriq/**"
+"target/ramips":
+  - "target/linux/ramips/**"
+"target/realtek":
+  - "target/linux/realtek/**"
+"target/rockchip":
+  - "target/linux/rockchip/**"
+"target/sunxi":
+  - "target/linux/sunxi/**"
+"target/tegra":
+  - "target/linux/tegra/**"
+"target/uml":
+  - "target/linux/uml/**"
+"target/x86":
+  - "target/linux/x86/**"
+"target/zynq":
+  - "target/linux/zynq/**"
+# target/imagebuilder
+"target/imagebuilder":
+  - "target/imagebuilder/**"
+# kernel
+"kernel":
+  - "target/linux/generic/**"
+  - "target/linux/**/config-*"
+  - "target/linux/**/patches-*"
+  - "target/linux/**/files/**"
+  - "package/kernel/linux/**"
+# core packages
+"core packages":
+  - "package/**"
+# build/scripts/tools
+"build/scripts/tools":
+  - "include/**"
+  - "scripts/**"
+  - "tools/**"
+# toolchain
+"toolchain":
+  - "toolchain/**"
+# GitHub/CI
+"GitHub/CI":
+  - ".github/**"