github: add issue templates file

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

.github/issue_template

@@ -0,0 +1,40 @@
+# Issue template:
+1. Please make sure that the issue subject starts with `<package-name>:`
+2. Issues related to end of life (EOL) releases are not supported or maintained and will be closed
+3. Remove lines from top till here and fill in the following questions
+***
+
+## Steps to reproduce:
+**Example: Replace the following lines and remove this**
+
+1. go to: Network → Interfaces → LAN (an interface with a static address) → DHCP server tab → IPv6 RA settings tab
+2. set RA MTU and RA Hop Limit to arbitrary non-default value
+3. Save & Apply
+4. go to: IPv6 RA settings tab again
+
+## Actual behavior:
+**Example: Replace the following lines and remove this**
+
+1. option ra_mtu '1500' is set correctly in /etc/config/dhcp
+2. In LuCI though, RA MTU and RA Hop Limit are still displaying the default values in light gray font color.
+
+## Expected behavior:
+**Example: Replace the following lines and remove this**
+
+```
+RA MTU and RA Hop Limit are displaying the correct values found in /etc/config/dhcp in black font color.
+```
+
+## Additional Information:
+OpenWrt version information from system `/etc/openwrt_release`
+
+**Example: Replace the following lines and remove this**
+```
+DISTRIB_ID='OpenWrt'
+DISTRIB_RELEASE='21.02.0-rc4'
+DISTRIB_REVISION='r16256-2d5ee43dc6'
+DISTRIB_TARGET='x86/64'
+DISTRIB_ARCH='x86_64'
+DISTRIB_DESCRIPTION='OpenWrt 21.02.0-rc4 r16256-2d5ee43dc6'
+DISTRIB_TAINTS=''
+```